Method and apparatus for interleaving bitstream to record thereof on a recording medium, and reproducing the interleaved bitstream therefrom

ABSTRACT

An interleaving method for generating a bitstream from plural video objects containing compressed video data by arranging in the presentation order, wherein interleaved data blocks in which plural video objects are contiguously arrayed using interleaved units each longer than the shortest read time ILVUMT such that the video object presentation start and end points are aligned. The ratio between the presentation times of video objects with the shortest presentation time and video objects other than those with the shortest presentation time is within a range obtained from the shortest read time ILVUMT, the maximum jumpable distance JM, and the smallest control unit. contiguous data blocks wherein the presentation start points and end points of the video objects arrayed therein are not aligned.

This is a Divisional of application Ser. No. 08/720,055, filed Sep. 27,1996 now U.S. Pat. No. 5,784,528.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for interleavinga bitstream for use in an authoring system for variously processing adata bitstream comprising the video data, audio data, and sub-picturedata constituting-each of plural program titles containing related videodata, audio data, and sub-picture data content to generate a bitstreamfrom which a new title containing the content desired by the user can bereproduced, and efficiently recording and reproducing said generatedbitstream using a particular recording medium.

2. Description of the Prior Art

Authoring systems used to produce program titles comprising relatedvideo data, audio data, and sub-picture data by digitally processing,for example, multimedia data comprising video, audio, and sub-picturedata recorded to laser disk or video CD formats are currently available.Systems using Video-Cds in particular are able to record video data to aCD format disk, which was originally designed with an approximately 600MB recording capacity for storing digital audio data only, by using suchhigh efficiency video compression techniques as MPEG. As a result of theincreased effective recording capacity achieved using data compressiontechniques, karaoke titles and other conventional laser diskapplications are gradually being transferred to the video CD format.Users today expect both sophisticated title content and highreproduction quality. To meet these expectations, each title must becomposed from bitstreams with an increasingly deep hierarchicalstructure. The data size of multimedia titles written with bitstreamshaving such deep hierarchical structures, however, is ten or more timesgreater than the data size of less complex titles. The need to editsmall image (title) details also makes it necessary to process andcontrol the bitstream using low order hierarchical data units.

It is therefore necessary to develop and prove a bitstream structure andan advanced digital processing method including both recording andreproduction capabilities whereby a large volume, multiple levelhierarchical digital bitstream can be efficiently controlled at eachlevel of the hierarchy. Also needed are an apparatus for executing thisdigital processing method, and a recording media to which the bitstreamdigitally processed by said apparatus can be efficiently recorded forstorage and from which said recorded information can be quicklyreproduced.

Means of increasing the storage capacity of conventional optical diskshave been widely researched to address the recording medium aspect ofthis problem. One way to increase the storage capacity of the opticaldisk is to reduce the spot diameter D of the optical (laser) beam. Ifthe wavelength of the laser beam is 1 and the aperture of the objectivelens is NA, then the spot diameter D is proportional to l/NA, and thestorage capacity can be efficiently improved by decreasing l andincreasing NA.

As described, for example, in U.S. Pat. No. 5,235,581, however, comacaused by a relative tilt between the disk surface and the optical axisof the laser beam (hereafter “tilt”) increases when a large aperture(high NA) lens is used. To prevent tilt-induced coma, the transparentsubstrate must be made very thin. The problem is that the mechanicalstrength of the disk is low when the transparent substrate is very thin.

MPEG1, the conventional method of recording and reproducing video,audio, and graphic signal data, has also been replaced by the morerobust MPEG2 method, which can transfer large data volumes at a higherrate. It should be noted that the compression method and data format ofthe MPEG2 standard differ somewhat from those of MPEG1. The specificcontent of and differences between MPEG1 and MPEG2 are described indetail in the ISO-11172 and ISO-13818 MPEG standards, and furtherdescription thereof is omitted below.

Note, however, that while the structure of the encoded video stream isdefined in the MPEG2 specification, the hierarchical structure of thesystem stream and the method of processing lower hierarchical levels arenot defined.

As described above, it is therefore not possible in a conventionalauthoring system to process a large data stream containing sufficientinformation to satisfy many different user requirements. Moreover, evenif such a processing method were available, the processed data recordedthereto cannot be repeatedly used to reduce data redundancy becausethere is no large capacity recording medium currently available that canefficiently record and reproduce high volume bitstreams such asdescribed above.

More specifically, particular significant hardware and softwarerequirements must be satisfied in order to process a bitstream using adata unit smaller than the title. These specific hardware requirementsinclude significantly increasing the storage capacity of the recordingmedium and increasing the speed of digital processing; softwarerequirements include inventing an advanced digital processing methodincluding a sophisticated data structure.

Therefore, the object of the present invention is to provide aneffective authoring system for controlling a multimedia data bitstreamwith advanced hardware and software requirements using a data unitsmaller than the title to better address advanced user requirements.

To share data between plural titles and thereby efficiently utilizeoptical disk capacity, multi-scene control whereby scene data common toplural titles and the desired scenes on the same time-base from withinmulti-scene periods containing plural scenes unique to particularreproduction paths can be freely selected and reproduced is desirable.

However, when plural scenes unique to a reproduction path within themulti-scene period are arranged on the same time-base, the scene datamust be contiguous. Unselected multi-scene data is therefore unavoidablyinserted between the selected common scene data and the selectedmulti-scene data. The problem this creates when reproducing multi-scenedata is that reproduction is interrupted by this unselected scene data.

The object of the present invention is therefore to provide a datastructure enabling discrete scene data to be seamlessly reproduced,i.e., without intermittency in the data presentation, even whenreproducing such multi-scene data; a method for generating a systemstream having said data structure; a recording apparatus and areproduction apparatus for recording and reproducing said system stream;and a medium to which said system stream can be recorded and from whichsaid system stream can be reproduced by said recording apparatus andreproduction apparatus.

To share data between plural titles and thereby efficiently utilizeoptical disk capacity, multi-scene control whereby scene data common toplural titles and the desired scenes on the same time-base from withinmulti-scene periods containing plural scenes unique to particularreproduction paths can be freely selected and reproduced is desirable.

However, when plural scenes unique to a reproduction path within themulti-scene period are arranged on the same time-base, the scene datamust be contiguous. Unselected multi-scene data is therefore unavoidablyinserted between the selected common scene data and the selectedmulti-scene data. The problem this creates when reproducing multi-scenedata is that reproduction is interrupted by this unselected scene data.

A further problem can be expected when the multi-scene data ismulti-angle scene data, i.e., scene data showing substantially the samesubject from different angles. In the case of a live sports broadcast,this multi-angle scene data may be obtained by recording a baseballbatter, for example, with cameras in different locations. The problem isthus that when the user selects one of these plural angle scenes duringdata presentation, data from different angles is connected where theangle changes, and a natural, seamless presentation cannot be expected.

Therefore, the object of the present invention is to provide a datastructure whereby natural, seamless reproduction without scene dataintermitting can be achieved even in such multi-angle scene periods; amethod for generating a system stream having said data structure; arecording apparatus and a reproduction apparatus for recording andreproducing said system stream; and a medium to which said system streamcan be recorded and from which said system stream can be reproduced bysaid recording apparatus and reproduction apparatus.

The present application is based upon Japanese Patent Application No.7-276714 and 8-041587, which were filed on Sep. 29, 1995 and Feb. 28,1996, respectively, the entire contents of which are expresslyincorporated by reference herein.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide an imagingdevice which solves these problems.

The present invention has been developed with a view to substantiallysolving the above described disadvantages and has for its essentialobject to provide an improved electrophotographic imaging device.

In order to achieve the aforementioned objective, an interleaving methodfor generating a bitstream from plural video objects containingcompressed video data by arranging in the presentation order, whereininterleaved data blocks in which plural video objects are contiguouslyarrayed using interleaved units each longer than the shortest read timeILVUMT such that the video object presentation start and end points arealigned, the ratio between the presentation times of video objects withthe shortest presentation time and video objects other than those withthe shortest presentation time is within a range obtained from theshortest read time ILVUMT, the maximum jumpable distance JM, and thesmallest control unit VOBU, and contiguous data blocks wherein thepresentation start points and end points of the video objects arrayedtherein are not aligned.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings throughout which like parts are designated by like referencenumerals, and in which:

FIG. 1 is a graph schematically showing a structure of multi media bitstream according to the present invention,

FIG. 2 is a block diagram showing an authoring encoder according to thepresent invention,

FIG. 3 is a block diagram showing an authoring decoder according to thepresent invention,

FIG. 4 is a side view of an optical disk storing the multi media bitstream of FIG. 1,

FIG. 5 is an enlarged view showing a portion confined by a circle ofFIG. 4,

FIG. 6 is an enlarged view showing a portion confined by a circle ofFIG. 5,

FIG. 7 is a side view showing a variation of the optical disk of FIG. 4,

FIG. 8 is a side view showing another variation of the optical disk ofFIG. 4,

FIG. 9 is a plan view showing one example of track path formed on therecording surface of the optical disk of FIG. 4,

FIG. 10 is a plan view showing another example of track path formed onthe recording surface of the optical disk of FIG. 4,

FIG. 11 is a diagonal view schematically showing one example of a trackpath pattern formed on the optical disk of FIG. 7,

FIG. 12 is a plan view showing another example of track path formed onthe recording surface of the optical disk of FIG. 7,

FIG. 13 is a diagonal view schematically showing one example of a trackpath pattern formed on the optical disk of FIG. 8,

FIG. 14 is a plan view showing another example of track path formed onthe recording surface of the optical disk of FIG. 8,

FIG. 15 is a graph showing the audio waves resulting from the audio datarecorded to the multi-angle data within multi-angle scene period,

FIG. 16 is a graph schematically showing the structure of multimedia bitstream for use in Digital Video Disk system according to the presentinvention,

FIG. 17 is a graph schematically showing the encoded video streamaccording to the present invention,

FIG. 18 is a graph schematically showing an internal structure of avideo zone of FIG. 16.

FIG. 19 is a graph schematically showing the stream managementinformation according to the present invention,

FIG. 20 is a graph schematically showing the structure the navigationpack NV of FIG. 17,

FIG. 21 is a graph is assistance of explaining a concept of parentallock playback control according to the present invention,

FIG. 22 is a graph schematically showing the data structure used in adigital video disk system according to the present invention,

FIG. 23 is a graph in assistance of explaining a concept of Multi-anglescene control according to the present invention,

FIG. 24 is a graph in assistance of explaining a concept of multi scenedata connection,

FIG. 25 is a block diagram showing a DVD encoder according to thepresent invention,

FIG. 26 is a block diagram showing a DVD decoder according to thepresent invention,

FIG. 27 is a graph schematically showing an encoding information tablegenerated by the encoding system controller of FIG. 25,

FIG. 28 is a graph schematically showing an encoding information tables,

FIG. 29 is a graph schematically showing an encoding parameters used bythe video encoder of FIG. 25,

FIG. 30 is a graph schematically showing an example of the contents ofthe program chain information according to the present invention,

FIG. 31 is a graph schematically showing another example of the contentsof the program chain information according to the present invention,

FIG. 32 is a graph schematically showing a relationship between theaccumulated data quantity in the stream buffer and the operating mode ofthe reading head of FIG. 26,

FIG. 33 is a graph in assistance of explaining a concept of sharing databetween plural titles,

FIG. 34 is a graph in assistance of explaining a concept of contiguousreproduction of non-contiguously arranged data block,

FIG. 35 is a graph in assistance of explaining a concept of interleavingprocess enabling seamless reproduction of scenes,

FIG. 36 is a graph also in assistance of explaining a concept ofinterleaving process enabling seamless reproduction of scenes,

FIG. 37 is a graph schematically showing an actual arrangement of datablocks recorded to a data recording track on a recording mediumaccording to the present invention,

FIG. 38 is a graph schematically showing contiguous block regions andinterleaved block regions array,

FIG. 39 is a graph schematically showing a content of a VTS title VOBS(VTSTT_VOBS) according to the present invention,

FIG. 40 is a graph schematically showing an internal data structure ofthe interleaved block regions according to the present invention,

FIG. 41 is a graph in assistance of explaining a concept of defining theminimum number of divisions in VOB for interleaving,

FIG. 42 is a graph schematically showing the data structure of theinterleaved unit,

FIG. 43 is a graph in assistance of explaining a concept of parentalcontrol according to the present invention,

FIG. 44 is a graph in assistance of explaining a concept of multi-anglescene control according to the present in invention,

FIG. 45 is a graph in assistance of explaining the multi-angle scenecontrol when two multi-angle data having different audio data,

FIG. 46 is a graph schematically showing plural angle data written tomulti-angle scene period according to the present invention,

FIG. 47 is a graph showing the stream containing a multi-angle sceneperiod and the basics of the on-disk layout according to the presentinvention,

FIG. 48 is a graph showing an example in which the last pack address inthe current A-ILVU and the address of the next A-ILVU are recorded forplural angles according to the present invention,

FIGS. 49 and 50 are graphs in assistance of explaining the method ofmanaging addresses on the switching unit level between multiple angledata in multi-angle scene periods according to the present invention,

FIG. 51 is a flow chart, formed by FIGS. 51A and 51B, showing anoperation of the DVD encoder of FIG. 25,

FIG. 52 is a flow chart showing detailed of the encode parameterproduction sub-routine of FIG. 51,

FIG. 53 is a flow chart showing the detailed of the VOB data settingroutine of FIG. 52,

FIG. 54 is a flow chart showing the encode parameters generatingoperation for a seamless switching,

FIG. 55 is a flow chart showing the encode parameters generatingoperation for a system stream,

FIG. 56 is a flow chart showing the operation of the DVD encoder of FIG.26,

FIG. 57 is a flow chart showing details of the multi-angle non-seamlessswitching control routine of FIG. 56,

FIG. 58 is a flow chart showing details of the multi-angle seamlessswitching control routine of FIG. 56,

FIG. 59 is a flow chart showing details of the parental lock sub-routineof FIG. 56,

FIG. 60 is a flow chart showing details of the single scene subroutineof FIG. 56,

FIG. 61 is a flow chart showing the encode parameters generatingoperation for a system stream containing a single scene,

FIGS. 62 and 63 are graphs showing decoding information table producedby the decoding system controller of FIG. 26,

FIG. 64 is a flow chart showing details of reproduction extracted PGCrouting of FIG. 69,

FIG. 65 is a flow chart showing details of non-seamless multi-angledecoding process of FIG. 70,

FIG. 66 is a block diagram showing details of the stream buffer of FIG.26,

FIG. 67 is a flow chart showing details of decoding data process of FIG.64, performed by the stream buffer, is shown,

FIG. 68 is a flow chart showing details of the decoder synchronizationprocess of FIG. 67,

FIG. 69 is a flow chart showing the operation of the DVD decoder DCD ofFIG. 26,

FIG. 70 is a flow chat showing details of the stream buffer datatransfer process according to the present invention,

FIG. 71 is a flow chart showing details of the non multi-angle decodingprocess of FIG. 70,

FIG. 72 is a flow chart showing details of the non-multi-angledinterleave process of FIG. 71,

FIG. 73 is a flow chart showing details of the non-multi-angledcontiguous block process,

FIG. 74 is a flow chart showing details of the non-multi-angle decodingprocess of FIG. 70,

FIG. 75 is a flow chart showing details of the seamless multi-angledecoding process of FIG. 70,

FIGS. 76 and 77 are graphs in assistance of explaining the switchingbetween scene angles within a multi-angle scene period,

FIG. 78 is a graph in assistance of explaining a method for achievingthe data structure shown in FIG. 46,

FIG. 79 is a graph in assistance of explaining a method for actuallysetting the audio data presentation times on the smallest angleswitching unit level to the same value in different angles, and

FIG. 80 is a graph in assistance of explaining the multi-angle sceneperiod data structure in which common audio data is written to eachdifferent angle according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Data Structure of theAuthoring System

The logic structure of the multimedia data bitstream processed using therecording apparatus, recording medium, reproduction apparatus, andauthoring system according to the present invention is described firstbelow with reference to FIG. 1.

In this structure, one title refers to the combination of video andaudio data expressing program content recognized by a user foreducation, entertainment, or other purpose. Referenced to a motionpicture (movie), one title may correspond to the content of an entiremovie, or to just one scene within said movie.

A video title set (VTS) comprises the bitstream data containing theinformation for a specific number of titles. More specifically, each VTScomprises the video, audio, and other reproduction data representing thecontent of each title in the set, and control data for controlling thecontent data.

The video zone VZ is the video data unit processed by the authoringsystem, and comprises a specific number of video title sets. Morespecifically, each video zone is a linear sequence of K+1 video titlesets numbered VTS #0-VTS #K where K is an integer value of zero orgreater. One video title set, preferably the first video title set VTS#0, is used as the video manager describing the content information ofthe titles contained in each video title set.

The multimedia bitstream MBS is the largest control unit of themultimedia data bitstream handled by the authoring system of the presentinvention, and comprises plural video zones VZ.

Authoring Encoder EC

A preferred embodiment of the authoring encoder EC according to thepresent invention for generating a new multimedia bitstream MBS byre-encoding the original multimedia bitstream MBS according to thescenario desired by the user is shown in FIG. 2. Note that the originalmultimedia bitstream MBS comprises a video stream St1 containing thevideo information, a sub-picture stream St3 containing caption text andother auxiliary video information, and the audio stream St5 containingthe audio information.

The video and audio streams are the bitstreams containing the video andaudio information obtained from the source within a particular period oftime. The sub-picture stream is a bitstream containing momentary videoinformation relevant to a particular scene. The sub-picture data encodedto a single scene may be captured to video memory and displayedcontinuously from the video memory for plural scenes as may benecessary.

When this multimedia source data St1, St3, and St5 is obtained from alive broadcast, the video and audio signals are supplied in real-timefrom a video camera or other imaging source; when the multimedia sourcedata is reproduced from a video tape or other recording medium, theaudio and video signals are not real-time signals.

While the multimedia source stream is shown in FIG. 2 as comprisingthese three source signals, this is for convenience only, and it shouldbe noted that the multimedia source stream may contain more than threetypes of source signals, and may contain source data for differenttitles. Multimedia source data with audio, video, and sub-picture datafor plural titles are referred to below as multi-title streams.

As shown in FIG. 2, the authoring encoder EC comprises a scenario editor100, encoding system controller 200, video encoder 300, video streambuffer 400, sub-picture encoder 500, sub-picture stream buffer 600,audio encoder 700, audio stream buffer 800, system encoder 900, videozone formatter 1300, recorder 1200, and recording medium M.

The video zone formatter 1300 comprises video object (VOB) buffer 1000,formatter 1100, and volume and file structure formatter 1400.

The bitstream encoded by the authoring encoder EC of the presentembodiment is recorded by way of example only to an optical disk.

The scenario editor 100 of the authoring encoder EC outputs the scenariodata, i.e., the user-defined editing instructions. The scenario datacontrols editing the corresponding parts of the multimedia bitstream MBSaccording to the user's manipulation of the video, sub-picture, andaudio components of the original multimedia title. This scenario editor100 preferably comprises a display, speaker(s), keyboard, CPU, andsource stream buffer. The scenario editor 100 is connected to anexternal multimedia bitstream source from which the multimedia sourcedata St1, St3, and St5 are supplied.

The user is thus able to reproduce the video and audio components of themultimedia source data using the display and speaker to confirm thecontent of the generated title. The user is then able to edit the titlecontent according to the desired scenario using the keyboard, mouse, andother command input devices while confirming the content of the title onthe display and speakers. The result of this multimedia datamanipulation is the scenario data St7.

The scenario data St7 is basically a set of instructions describing whatsource data is selected from all or a subset of the source datacontaining plural titles within a defined time period, and how theselected source data is reassembled to reproduce the scenario (sequence)intended by the user. Based on the instructions received through thekeyboard or other control device, the CPU codes the position, length,and the relative time-based positions of the edited parts of therespective multimedia source data streams St1, St3, and St5 to generatethe scenario data St7.

The source stream buffer has a specific capacity, and is used to delaythe multimedia source data streams St1, St3, and St5 a known time Td andthen output streams St1, St3, and St5.

This delay is required for synchronization with the editor encodingprocess. More specifically, when data encoding and user generation ofscenario data St7 are executed simultaneously, i.e., when encodingimmediately follows editing, time Td is required to determine thecontent of the multimedia source data editing process based on thescenario data St7 as will be described further below. As a result, themultimedia source data must be delayed by time Td to synchronize theediting process during the actual encoding operation. Because this delaytime Td is limited to the time required to synchronize the operation ofthe various system components in the case of sequential editing asdescribed above, the source stream buffer is normally achieved by meansof a high speed storage medium such as semiconductor memory.

During batch editing in which all multimedia source data is encoded atonce (“batch encoded”) after scenario data St7 is generated for thecomplete title, delay time Td must be long enough to process thecomplete title or longer. In this case, the source stream buffer may bea low speed, high capacity storage medium such as video tape, magneticdisk, or optical disk.

The structure (type) of media used for the source stream buffer maytherefore be determined according to the delay time Td required and theallowable manufacturing cost.

The encoding system controller 200 is connected to the scenario editor100 and receives the scenario data St7 therefrom. Based on the time-baseposition and length information of the edit segment contained in thescenario data St7, the encoding system controller 200 generates theencoding parameter signals St9, St11, and St13 for encoding the editsegment of the multimedia source data. The encoding signals St9, St11,and St13 supply the parameters used for video, sub-picture, and audioencoding, including the encoding start and end timing. Note thatmultimedia source data St1, St3, and St5 are output after delay time Tdby the source stream buffer, and are therefore synchronized to encodingparameter signals St9, St11, and St13.

More specifically, encoding parameter signal St9 is the video encodingsignal specifying the encoding timing of video stream St1 to extract theencoding segment from the video stream St1 and generate the videoencoding unit. Encoding parameter signal st11 is likewise thesub-picture stream encoding signal used to generate the sub-pictureencoding unit by specifying the encoding timing for sub-picture streamSt3. Encoding parameter signal St13 is the audio encoding signal used togenerate the audio encoding unit by specifying the encoding timing foraudio stream St5.

Based on the time-base relationship between the encoding segments ofstreams St1, St3, and St5 in the multimedia source data contained inscenario data St7, the encoding system controller 200 generates thetiming signals St21, St23, and St25 arranging the encodedmultimedia-encoded stream in the specified time-base relationship.

The encoding system controller 200 also generates the reproduction timeinformation IT defining the reproduction time of the title editing unit(video object, VOB), and the stream encoding data St33 defining thesystem encode parameters for multiplexing the encoded multimedia streamcontaining video, audio, and sub-picture data. Note that thereproduction time information IT and stream encoding data St33 aregenerated for the video object VOB of each title in one video zone VZ.

The encoding system controller 200 also generates the title sequencecontrol signal St39, which declares the formatting parameters forformatting the title editing units VOB of each of the streams in aparticular time-base relationship as a multimedia bitstream. Morespecifically, the title sequence control signal St39 is used to controlthe connections between the title editing units (VOB) of each title inthe multimedia bitstream MBS, or to control the sequence of theinterleaved title editing unit (VOBs) interleaving the title editingunits VOB of plural reproduction paths.

The video encoder 300 is connected to the source stream buffer of-thescenario editor 100 and to the encoding system controller 200, andreceives therefrom the video stream St1 and video encoding parametersignal St9, respectively. Encoding parameters supplied by the videoencoding signal St9 include the encoding start and end timing, bit rate,the encoding conditions for the encoding start and end, and the materialtype. Possible material types include NTSC or PAL video signal, andtelecine converted material. Based on the video encoding parametersignal St9, the video encoder 300 encodes a specific part of the videostream St1 to generate the encoded video stream St15.

The sub-picture encoder 500 is similarly connected to the source streambuffer of the scenario editor 100 and to the encoding system controller200, and receives therefrom the sub-picture stream St3 and sub-pictureencoding parameter signal St11, respectively. Based on the sub-pictureencoding parameter signal St11, the sub-picture encoder 500 encodes aspecific part of the sub-picture stream St3 to generate the encodedsub-picture stream St17.

The audio encoder 700 is also connected to the source stream buffer ofthe scenario editor 100 and to the encoding system controller 200, andreceives therefrom the audio stream St5 and audio encoding parametersignal St13, which supplies the encoding start and end timing. Based onthe audio encoding parameter signal St13, the audio encoder 700 encodesa specific part of the audio stream St5 to generate the encoded audiostream St19.

The video stream buffer 400 is connected to the video encoder 300 and tothe encoding system controller 200. The video stream buffer 400 storesthe encoded video stream St15 input from the video encoder 300, andoutputs the stored encoded video stream St15 as the time-delayed encodedvideo stream St27 based on the timing signal St1 supplied from theencoding system controller 200.

The sub-picture stream buffer 600 is similarly connected to thesub-picture encoder 500 and to the encoding system controller 200. Thesub-picture stream buffer 600 stores the encoded sub-picture stream St17output from the sub-picture encoder 500, and then outputs the storedencoded sub-picture stream St17 as time-delayed encoded sub-picturestream St29 based on the timing signal St23 supplied from the encodingsystem controller 200.

The audio stream buffer 800 is similarly connected to the audio encoder700 and to the encoding system controller 200. The audio stream buffer800 stores the encoded audio stream St19 input from the audio encoder700, and then outputs the encoded audio stream St19 as the time-delayedencoded audio stream St31 based on the timing signal St25 supplied fromthe encoding system controller 200.

The system encoder 900 is connected to the video stream buffer 400,sub-picture stream buffer 600, audio stream buffer 800, and the encodingsystem controller 200, and is respectively supplied thereby with thetime-delayed encoded video stream St27, time-delayed encoded sub-picturestream St29, time-delayed encoded audio stream St31, and the streamencoding data St33. Note that the system encoder 900 is a multiplexerthat multiplexes the time-delayed streams St27, St29, and St31 based onthe stream encoding data St33 (timing signal) to generate title editingunit (VOB) St35. The stream encoding data St33 contains the systemencoding parameters, including the encoding start and end timing.

The video zone formatter 1300 is connected to the system encoder 900 andthe encoding system controller 200 from which the title editing unit(VOB) St35 and title sequence control signal St39 (timing signal) arerespectively supplied. The title sequence control signal St39 containsthe formatting start and end timing, and the formatting parameters usedto generate (format) a multimedia bitstream MBS. The video zoneformatter 1300 rearranges the title editing units (VOB) St35 in onevideo zone VZ in the scenario sequence defined by the user based on thetitle sequence control signal St39 to generate the edited multimediastream data St43.

The multimedia bitstream MBS St43 edited according to the user-definedscenario is then sent to the recorder 1200. The recorder 1200 processesthe edited multimedia stream data St43 to the data stream St45 format ofthe recording medium M, and thus records the formatted data stream St45to the recording medium M. Note that the multimedia bitstream MBSrecorded to the recording medium M contains the volume file structureVFS, which includes the physical address of the data on the recordingmedium generated by the video zone formatter 1300.

Note that the encoded multimedia bitstream MBS St35 may be outputdirectly to the decoder to immediately reproduce the edited titlecontent. It will be obvious that the output multimedia bitstream MBSwill not in this case contain the volume file structure VFS.

Authoring Decoder

A preferred embodiment of the authoring decoder DC used to decode themultimedia bitstream MBS edited by the authoring encoder EC of thepresent invention, and thereby reproduce the content of each title unitaccording to the user-defined scenario is described next below withreference to FIG. 3. Note that in the preferred embodiment describedbelow the multimedia bitstream St45 encoded by the authoring encoder ECis recorded to the recording medium M.

As shown in FIG. 3, the authoring decoder DC comprises a multimediabitstream producer 2000, scenario selector 2100, decoding systemcontroller 2300, stream buffer 2400, system decoder 2500, video buffer2600, sub-picture buffer 2700, audio buffer 2800, synchronizer 2900,video decoder 3800, sub-picture decoder 3100, audio decoder 3200,synthesizer 3500, video data output terminal 3600, and audio data outputterminal 3700.

The bitstream producer 2000 comprises a recording media drive unit 2004for driving the recording medium M; a reading head 2006 for reading theinformation recorded to the recording medium M and producing the binaryread signal St57; a signal processor 2008 for variously processing theread signal St57 to generate the reproduced bitstream St61; and areproduction controller 2002.

The reproduction controller 2002 is connected to the decoding systemcontroller 2300 from which the multimedia bitstream reproduction controlsignal St53 is supplied, and in turn generates the reproduction controlsignals St55 and St59 respectively controlling the recording media driveunit (motor) 2004 and signal processor 2008.

So that the user-defined video, sub-picture, and audio portions of themultimedia title edited by the authoring encoder EC are reproduced, theauthoring decoder DC comprises a scenario selector 2100 for selectingand reproducing the corresponding scenes (titles). The scenario selector2100 then outputs the selected titles as scenario data to the authoringdecoder DC.

The scenario selector 2100 preferably comprises a keyboard, CPU, andmonitor. Using the keyboard, the user then inputs the desired scenariobased on the content of the scenario input by the authoring encoder EC.Based on the keyboard input, the CPU generates the scenario selectiondata St51 specifying the selected scenario. The scenario selector 2100is connected by an infrared communications device, for example, to thedecoding system controller 2300, to which it inputs the scenarioselection data St51.

Based on the scenario selection data St51, the decoding systemcontroller 2300 then generates the bitstream reproduction control signalSt53 controlling the operation of the bitstream producer 2000.

The stream buffer 2400 has a specific buffer capacity used totemporarily store the reproduced bitstream St61 input from the bitstreamproducer 2000, extract the address information and initialsynchronization data SCR (system clock reference) for each stream, andgenerate bitstream control data St63. The stream buffer 2400 is alsoconnected to the decoding system controller 2300, to which it suppliesthe generated bitstream control data St63.

The synchronizer 2900 is connected to the decoding system controller2300 from which it receives the system clock reference SCR contained inthe synchronization control data St81 to set the internal system clockSTC and supply the reset system clock St79 to the decoding systemcontroller 2300.

Based on this system clock St79, the decoding system controller 2300also generates the stream read signal St65 at a specific interval andoutputs the read signal St65 to the stream buffer 2400.

Based on the supplied read signal St65, the stream buffer 2400 outputsthe reproduced bitstream St61 at a specific interval to the systemdecoder 2500 as bitstream St67.

Based on the scenario selection data St51, the decoding system-controller 2300 generates the decoding signal St69 defining the streamIds for the video, sub-picture, and audio bitstreams corresponding tothe selected scenario, and outputs to the system decoder 2500.

Based on the instructions contained in the decoding signal St69, thesystem decoder 2500 respectively outputs the video, sub-picture, andaudio bitstreams input from the stream buffer 2400 to the video buffer2600, sub-picture buffer 2700, and audio buffer 2800 as the encodedvideo stream St71, encoded sub-picture stream St73, and encoded audiostream St75.

The system decoder 2500 detects the presentation time stamp PTS anddecoding time stamp DTS of the smallest control unit in each bitstreamSt67 to generate the time information signal St77. This time informationsignal St77 is supplied to the synchronizer 2900 through the decodingsystem controller 2300 as the synchronization control data St81.

Based on this synchronization control data St81, the synchronizer 2900determines the decoding start timing whereby each of the bitstreams willbe arranged in the correct sequence after decoding, and then generatesand inputs the video stream decoding start signal St89 to the videodecoder 3800 based on this decoding timing. The synchronizer 2900 alsogenerates and supplies the sub-picture decoding start signal St91 andaudio stream decoding start signal St93 to the sub-picture decoder 3100and audio decoder 3200, respectively.

The video decoder 3800 generates the video output request signal St84based on the video stream decoding start signal St89, and outputs to thevideo buffer 2600. In response to the video output request signal St84,the video buffer 2600 outputs the video stream St83 to the video decoder3800. The video decoder 3800 thus detects the presentation timeinformation contained in the video stream St83, and disables the videooutput request signal St84 when the length of the received video streamSt83 is equivalent to the specified presentation time. A video streamequal in length to the specified presentation time is thus decoded bythe video decoder 3800, which outputs the reproduced video signal St104to the synthesizer 3500.

The sub-picture decoder 3100 similarly generates the sub-picture outputrequest signal St86 based on the sub-picture decoding start signal St91,and outputs to the sub-picture buffer 2700. In response to thesub-picture output request signal St86, the sub-picture buffer 2700outputs the sub-picture stream St85 to the sub-picture decoder 3100.Based on the presentation time information contained in the sub-picturestream St85, the sub-picture decoder 3100 decodes a length of thesub-picture stream St85 corresponding to the specified presentation timeto reproduce and supply to the synthesizer 3500 the sub-picture signalst99.

The synthesizer 3500 superimposes the video signal St104 and sub-picturesignal st99 to generate and output the multi-picture video signal St105to the video data output terminal 3600.

The audio decoder 3200 generates and supplies to the audio buffer 2800the audio output request signal St88 based on the audio stream decodingstart signal St93. The audio buffer 2800 thus outputs the audio streamSt87 to the audio decoder 3200. The audio decoder 3200 decodes a lengthof the audio stream St87 corresponding to the specified presentationtime based on the presentation time information contained in the audiostream St87, and outputs the decoded audio stream St101 to the audiodata output terminal 3700.

It is thus possible to reproduce a user-defined multimedia bitstream MBSin real-time according to a user-defined scenario. More specifically,each time the user selects a different scenario, the authoring decoderDC is able to reproduce the title content desired by the user in thedesired sequence by reproducing the multimedia bitstream MBScorresponding to the selected scenario.

It is therefore possible by means of the authoring system of the presentinvention to generate a multimedia bitstream according to pluraluser-defined scenarios by real-time or batch encoding multimedia sourcedata in a manner whereby the substreams of the smallest editing units(scenes), which can be divided into plural substreams, expressing thebasic title content are arranged in a specific time-base relationship.

The multimedia bitstream thus encoded can then be reproduced accordingto the one scenario selected from among plural possible scenarios. It isalso possible to change scenarios while playback is in progress, i.e.,to select a different scenario and dynamically generate a new multimediabitstream according to the most recently selected scenario. It is alsopossible to dynamically select and reproduce any of plural scenes whilereproducing the title content according to a desired scenario.

It is therefore possible by means of the authoring system of the presentinvention to encode and not only reproduce but to repeatedly reproduce amultimedia bitstream MBS in real-time.

A detail of the authoring system is disclosed Japanese PatentApplication filed Sep. 27, 1996, and entitled and assigned to the sameassignee as the present application.

Digital Video Disk (DVD)

An example of a digital video disk (DVD) with only one recording surface(a single-sided DVD) is shown in FIG. 4.

The DVD recording medium RC1 in the preferred embodiment of theinvention comprises a data recording surface RS1 to and from which datais written and read by emitting laser beam LS, and a protective layerPL1 covering the data recording surface RS1. A backing layer BL1 is alsoprovided on the back of data recording surface RS1. The side of the diskon which protective layer PL1 is provided is therefore referred to belowas side SA (commonly “side A”), and the opposite side (on which thebacking layer BL1 is provided) is referred to as side SB (“side B”).Note that digital video disk recording media having a single datarecording surface RS1 on only one side such as this DVD recording mediumRC1 is commonly called a single-sided single layer disk.

A detailed illustration of area C1 in FIG. 4 is shown in FIG. 5. Notethat the data recording surface RS1 is formed by applying a metallicthin film or other reflective coating as a data layer 4109 on a firsttransparent layer 4108 having a particular thickness T1. This firsttransparent layer 4108 also functions as the protective layer PL1. Asecond transparent substrate 4111 of a thickness T2 functions as thebacking layer BL1, and is bonded to the first transparent layer 4108 bymeans of an adhesive layer 4110 disposed therebetween.

A printing layer 4112 for printing a disk label may also be disposed onthe second transparent substrate 4111 as necessary. The printing layer4112 does not usually cover the entire surface area of the secondtransparent substrate 4111 (backing layer BL1), but only the area neededto print the text and graphics of the disk label. The area of secondtransparent substrate 4111 to which the printing layer 4112 is notformed may be left exposed. Light reflected from the data layer 4109(metallic thin film) forming the data recording surface RS1 cantherefore be directly observed where the label is not printed when thedigital video disk is viewed from side SB. As a result, the backgroundlooks like a silver-white over which the printed text and graphics floatwhen the metallic thin film is an aluminum thin film, for example.

Note that it is only necessary to provide the printing layer 4112 whereneeded for printing, and it is not necessary to provide the printinglayer 4112 over the entire surface of the backing layer BL1.

A detailed illustration of area C2 in FIG. 5 is shown in FIG. 6. Pitsand lands are molded to the common contact surface between the firsttransparent layer 4108 and the data layer 4109 on side SA from whichdata is read by emitting a laser beam LS, and data is recorded byvarying the lengths of the pits and lands (i.e., the length of theintervals between the pits). More specifically, the pit and landconfiguration formed on the first transparent layer 4108 is transferredto the data layer 4109. The lengths of the pits and lands is shorter,and the pitch of the data tracks formed by the pit sequences isnarrower, than with a conventional Compact Disc (CD). The surfacerecording density is therefore greatly improved.

Side SA of the first transparent layer 4108 on which data pits are notformed is a flat surface. The second transparent substrate 4111 is forreinforcement, and is a transparent panel made from the same material asthe first transparent layer 4108 with both sides flat. Thicknesses T1and T2 are preferably equal and commonly approximately 0.6 mm, but theinvention shall not be so limited.

As with a CD, information is read by irradiating the surface with alaser beam LS and detecting the change in the reflectivity of the lightspot. Because the objective lens aperture NA can be large and thewavelength l of the light beam small in a digital video disk system, thediameter of the light spot Ls used can be reduced to approximately{fraction (1/1.6)} the light spot needed to read a CD. Note that thismeans the resolution of the laser beam LS in the DVD system isapproximately 1.6 times the resolution of a conventional CD system.

The optical system used to read data from the digital video disk uses ashort 650 nm wavelength red semiconductor laser and an objective lenswith a 0.6 mm .aperture NA. By thus also reducing the thickness T of thetransparent panels to 0.6 mm, more than 5 GB of data can be stored toone side of a 120 mm diameter optical disk.

It is therefore possible to store motion picture (video) images havingan extremely large per unit data size to a digital video disk systemdisk without losing image quality because the storage capacity of asingle-sided, single-layer recording medium RC1 with one data recordingsurface RS1 as thus described is nearly ten times the storage capacityof a conventional CD. As a result, while the video presentation time ofa conventional CD system is approximately 74 minutes if image quality issacrificed, high quality video images with a video presentation timeexceeding two hours can be recorded to a DVD.

The digital video disk is therefore well-suited as a recording mediumfor video images.

A digital video disk recording medium with plural recording surfaces RSas described above is shown in FIGS. 7 and 8. The DVD recording mediumRC2 shown in FIG. 7 comprises two recording surfaces, i.e., firstrecording surface RS1 and semi-transparent second recording surface RS2,on the same side, i.e. side SA, of the disk. Data can be simultaneouslyrecorded or reproduced from these two recording surfaces by usingdifferent laser beams LS1 and LS2 for the first recording surface RS1and the second recording surface RS2. It is also possible to read/writeboth recording surfaces RS1 and RS2 using only one of the laser beamsLS1 or LS2. Note that recording media thus comprised are called“single-side, dual-layer disks.”

It should also be noted that while two recording surfaces RS1 and RS2are provided in this example, it is also possible to produce digitalvideo disk recording media having more than two recording surfaces RS.Disks thus comprised are known as “single-sided, multi-layer disks.”

Though comprising two recording surfaces similarly to the recordingmedia shown in FIG. 7, the DVD recording medium RC3 shown in FIG. 8 hasthe recording surfaces on opposite sides of the disk, i. e., has thefirst data recording surface RS1 on side SA and the second datarecording surface RS2 on side SB. It will also be obvious that whileonly two recording surfaces are shown on one digital video disk in thisexample, more than two recording surfaces may also be formed on adouble-sided digital video disk. As with the recording medium shown inFIG. 7, it is also possible to provide two separate laser beams LS1 andLS2 for recording surfaces RS1 and RS2, or to read/write both recordingsurfaces RS1 and RS2 using a single laser beam. Note that this type ofdigital video disk is called a “double-sided, dual-layer disk.” It willalso be obvious that a double-sided digital video disk can be comprisedwith two or more recording surfaces per side. This type of disk iscalled a “double-sided, multi-layer disk.”

A plan view from the laser beam LS irradiation side of the recordingsurface RS of the DVD recording medium RC is shown in FIG. 9 and FIG.10. Note that a continuous spiral data recording track TR is providedfrom the inside circumference to the outside circumference of the DVD.The data recording track TR is divided into plural sectors each havingthe same known storage capacity. Note that for simplicity only the datarecording track TR is shown in FIG. 9 with more than three sectors perrevolution.

As shown in FIG. 9, the data recording track TR is normally formedclockwise inside to outside (see arrow DrA) from the inside end point IAat the inside circumference of disk RCA to the outside end point OA atthe outside circumference of the disk with the disk RCA rotatingcounterclockwise RdA. This type of disk RCA is called a clockwise disk,and the recording track formed thereon is called a clockwise track TRA.

Depending upon the application, the recording track TRB may be formedclockwise from outside to inside circumference (see arrow DrB in FIG.10) from the outside end point OB at the outside circumference of diskRCB to the inside end point IB at the inside circumference of the diskwith the disk RCB rotating clockwise RdB. Because the recording trackappears to wind counterclockwise when viewed from the insidecircumference to the outside circumference on disks with the recordingtrack formed in the direction of arrow DrB, these disks are referred toas counterclockwise disk RCB with counterclockwise track TRB todistinguish them from disk RCA in FIG. 9. Note that track directions DrAand DrB are the track paths along which the laser beam travels whenscanning the tracks for recording and playback. Direction of diskrotation RdA in which disk RCA turns is thus opposite the direction oftrack path DrA, and direction of disk rotation RdB in which disk RCBturns is thus opposite the direction of track path DrB.

An exploded view of the single-sided, dual-layer disk RC2 shown in FIG.7 is shown as disk RC2 o in FIG. 11. Note that the recording tracksformed on the two recording surfaces run in opposite directions.Specifically, a clockwise recording track TRA as shown in FIG. 9 isformed in clockwise direction DrA on the (lower) first data recordingsurface RS1, and a counterclockwise recording track TRB formed incounterclockwise direction DrB as shown in FIG. 10 is provided on the(upper) second data recording surface RS2. As a result, the outside endpoints OA and OB of the first and second (top and bottom) tracks are atthe same radial position relative to the center axis of the disk RC2 o.Note that track paths DrA and DrB of tracks TR are also the dataread/write directions to disk RC. The first and second (top and bottom)recording tracks thus wind opposite each other with this disk RC, i.e.,the track paths DrA and DrB of the top and bottom recording layers areopposite track paths.

Opposite track path type, single-sided, dual-layer disks RC2 o rotate indirection RdA corresponding to the first recording surface RS1 with thelaser beam LS travelling along track path DrA to trace the recordingtrack on the first recording surface RS1. When the laser beam LS reachesthe outside end point OA, the laser beam LS can be refocused to endpoint OB on the second recording surface RS2 to continue tracing therecording track from the first to the second recording surfaceuninterrupted. The physical distance between the recording tracks TRAand TRB on the first and second recording surfaces RS1 and RS2 can thusbe instantaneously eliminated by simply adjusting the focus of the laserbeam LS.

It is therefore possible with an opposite track path type, single-sided,dual-layer disk RC2 o to easily process the recording tracks disposed tophysically discrete top and bottom recording surfaces as a singlecontinuous recording track. It is therefore also possible in anauthoring system as described above with reference to FIG. 1 tocontinuously record the multimedia bitstream MBS that is the largestmultimedia data management unit to two discrete recording surfaces RS1and RS2 on a single recording medium RC2 o.

It should be noted that the tracks on recording surfaces RS1 and RS2 canbe wound in the directions opposite those described above, i.e., thecounterclockwise track TRB may be provided on the first recordingsurface RS1 and the clockwise track TRA on the second recording surfaceRS2. In this case the direction of disk rotation is also changed to aclockwise rotation RdB, thereby enabling the two recording surfaces tobe used as comprising a single continuous recording track as describedabove. For simplification, a further example of this type of disk istherefore neither shown nor described below.

It is therefore possible by thus constructing the digital video disk torecord the multimedia bitstream MBS for a feature-length title to asingle opposite track path type, single-sided, dual-layer disk RC2 o.Note that this type of digital video disk medium is called asingle-sided dual-layer disk with opposite track paths.

Another example of the single-sided, dual-layer DVD recording medium RC2shown in FIG. 7 is shown as disk RC2p in FIG. 12. The recording tracksformed on both first and second recording surfaces RS1 and RS2 areclockwise tracks TRA as shown in FIG. 9. In this case, the single-sided,dual-layer disk RC2 p rotates counterclockwise in the direction of arrowRdA, and the direction of laser beam LS travel is the same as thedirection of the track spiral, i.e., the track paths of the top andbottom recording surfaces are mutually parallel (parallel track paths).The outside end points OA of both top and bottom tracks are againpreferably positioned at the same radial position relative to the centeraxis of the disk RC2 p as described above. As also described above withdisk RC2 o shown in FIG. 11, the access point can be instantaneouslyshifted from outside end point OA of track TRA on the first recordingsurface RS1 to the outside end point OA of track TRA on the secondrecording surface RS2 by appropriately adjusting the focus of the laserbeam LS at outside end point OA.

However, for the laser beam LS to continuously access the clockwiserecording track TRA on the second recording surface RS2, the recordingmedium RC2 p must be driven in the opposite direction (clockwise,opposite direction RdA). Depending on the radial position of the laserbeam LS, however, it is inefficient to change the rotational directionof the recording medium. As shown by the diagonal arrow in FIG. 12, thelaser beam LS is therefore moved from the outside end point OA of thetrack on the first recording surface RS1 to the inside end point IA ofthe track on the second recording surface RS2 to use these physicallydiscrete recording tracks as one logically continuous recording track.

Rather than using the recording tracks on top and bottom recordingsurfaces as one continuous recording track, it is also possible to usethe recording tracks to record the multimedia bitstreams MBS fordifferent titles. This type of digital video disk recording medium iscalled a “single-sided, dual-layer disk with parallel track paths.”

Note that if the direction of the tracks formed on the recordingsurfaces RS1 and RS2 is opposite that described above, i.e.,counterclockwise recording tracks TRB are formed, disk operation remainsthe same as that described above except for the direction of diskrotation, which is clockwise as shown by arrow RdB.

Whether using clockwise or counterclockwise recording tracks, thesingle-sided, dual-layer disk RC2 p with parallel track paths thusdescribed is well-suited to storing on a single disk encyclopedia andsimilar multimedia bitstreams comprising multiple titles that arefrequently and randomly accessed.

An exploded view of the dual-sided single-layer DVD recording medium RC3comprising one recording surface layer RS1 and RS2 on each side as shownin FIG. 8 is shown as DVD recording medium RC3s in FIG. 13. Clockwiserecording track TRA is provided on the one recording surface RS1, and acounterclockwise recording track TRB is provided on the other recordingsurface RS2. As in the preceding recording media, the outside end pointsOA and OB of the recording tracks on each recording surface arepreferably positioned at the same radial position relative to the centeraxis of the DVD recording medium RC3s.

Note that while the recording tracks on these recording surfaces RS1 andRS2 rotate in opposite directions, the track-paths are symmetrical. Thistype of recording medium is therefore known as a double-sided dual layerdisk with symmetrical track paths. This double-sided dual layer diskwith symmetrical track paths RC3s rotates in direction RdA whenreading/writing the first recording surface RS1. As a result, the trackpath on the second recording surface RS2 on the opposite side isopposite the direction DrB in which the track winds, i.e., directionDrA. Accessing both recording surfaces RS1 and RS2 using a single laserbeam LS is therefore not realistic irrespective of whether access iscontinuous or non-continuous. In addition, a multimedia bitstream MBS isseparately recorded to the recording surfaces on the first and secondsides of the disk.

A different example of the double-sided single layer disk RC3 shown inFIG. 8 is shown in FIG. 14 as disk RC3 a. Note that this disk comprisesclockwise recording tracks TRA as shown in FIG. 9 on both recordingsurfaces RS1 and RS2. As with the preceding recording media, the outsideend points OA and OA of the recording tracks on each recording surfaceare preferably positioned at the same radial position relative to thecenter axis of the DVD recording medium RC3 a. Unlike the double-sideddual layer disk with symmetrical track paths RC3 s described above, thetracks on these recording surfaces RS1 and RS2 are asymmetrical. Thistype of disk is therefore known as a double-sided dual layer disk withasymmetrical track paths. This double-sided dual layer disk withasymmetrical track paths RC3 a rotates in direction RdA whenreading/writing the first recording surface RS1. As a result, the trackpath on the second recording surface RS2 on the opposite side isopposite the direction DrA in which the track winds, i.e., directionDrB.

This means that if a laser beam LS is driven continuously from theinside circumference to the outside circumference on the first recordingsurface RS1, and then from the outside circumference to the insidecircumference on the second recording surface RS2, both sides of therecording medium RC3 a can be read/written without turning the disk overand without providing different laser beams for the two sides.

The track paths for recording surfaces RS1 and RS2 are also the samewith this double-sided dual layer disk with asymmetrical track paths RC3a. As a result, it is also possible to read/write both sides of the diskwithout providing separate laser beams for each side if the recordingmedium RC3 a is turned over between sides, and the read/write apparatuscan therefore be constructed economically.

It should be noted that this recording medium remains functionallyidentical even if counterclockwise recording track TRB is provided inplace of clockwise recording track TRA on both recording surfaces RS1and RS2.

As described above, the true value of a DVD system whereby the storagecapacity of the recording medium can be easily increased by using amultiple layer recording surface is realized in multimedia applicationswhereby plural video data units, plural audio data units, and pluralgraphics data units recorded to a single disk are reproduced throughinteractive operation by the user.

It is therefore possible to achieve one long-standing desire of software(programming) providers, specifically, to provide programming contentsuch as a commercial movie on a single recording medium in pluralversions for different language and demographic groups while retainingthe image quality of the original.

Parental Control

Content providers of movie and video titles have conventionally had toproduce, supply, and manage the inventory of individual titles inmultiple languages, typically the language of each distribution market,and multi-rated title packages conforming to the parental control(censorship) regulations of individual countries in Europe and NorthAmerica. The time and resources required for this are significant. Whilehigh image quality is obviously important, the programming content mustalso be consistently reproducible.

The digital video disk recording medium is close to solving theseproblems.

Multiple Angles

One interactive operation widely sought in multimedia applications todayis for the user to be able to change the position from which a scene isviewed during reproduction of that scene. This capability is achieved bymeans of the multiple angle function.

This multiple angle function makes possible applications whereby, forexample, a user can watch a baseball game from different angles (orvirtual positions in the stadium), and can freely switch between theviews while viewing is in progress. In this example of a baseball game,the available angles may include a position behind the backstop centeredon the catcher, batter, and pitcher; one from behind the backstopcentered on a fielder, the pitcher, and the catcher; and one from centerfield showing the view to the pitcher and catcher.

To meet these requirements, the digital video disk system uses MPEG, thesame basic standard format used with Video-Cds to record the video,audio, graphics, and other signal data. Because of the differences instorage capacity, transfer rates, and signal processing performancewithin the reproduction apparatus, DVD uses MPEG2, the compressionmethod and data format of which differ slightly from the MPEG1 formatused with Video-Cds.

It should be noted that the content of and differences between the MPEG1and MPEG2 standards have no direct relationship to the intent of thepresent invention, and further description is therefore omitted below(for more information, see MPEG specifications ISO-11172 and ISO-13818).

The data structure of the DVD system according to the present inventionis described in detail below with reference to FIGS. 16, 17, 18, 19, 20,and 21.

Multi-scene Control

A fully functional and practical parental lock playback function andmulti-angle scene playback function must enable the user to modify thesystem output in minor, subtle ways while still presenting substantiallythe same video and audio output. If these functions are achieved bypreparing and recording separate titles satisfying each of the manypossible parental lock and multi-angle scene playback requests, titlesthat are substantially identical and differ in only minor ways must berecorded to the recording medium. This results in identical data beingrepeatedly recorded to the larger part of the recording medium, andsignificantly reduces the utilization efficiency of the availablestorage capacity. More particularly, it is virtually impossible torecord discrete titles satisfying every possible request even using themassive capacity of the digital video disk medium. While it may beconcluded that this problem can be easily solved by increasing thecapacity of the recording medium, this is an obviously undesirablesolution when the effective use of available system resources isconsidered.

Using multi-scene control, the concept of which is described in anothersection below, in a DVD system, it is possible to dynamically constructtitles for numerous variations of the same basic content using thesmallest possible amount of data, and thereby effectively utilize theavailable system resources (recording medium). More specifically, titlesthat can be played back with numerous variations are constructed frombasic (common) scene periods containing data common to each title, andmulti-scene periods comprising groups of different scenes correspondingto the various requests. During reproduction, the user is able to freelyand at any time select particular scenes from the multi-scene periods todynamically construct a title conforming to the desired content, e. g. ,a title omitting certain scenes using the parental lock controlfunction.

Note that multi-scene control enabling a parental lock playback controlfunction and multi-angle scene playback is described in another sectionbelow with reference to FIG. 21.

Data Structure of the DVD System

The data structure used in the authoring system of a digital video disksystem according to the present invention is shown in FIG. 22. To recorda multimedia bitstream MBS, this digital video disk system divides therecording medium into three major recording areas, the lead-in area LI,the volume space VS, and the lead-out area LO.

The lead-in area LI is provided at the inside circumference area of theoptical disk. In the disks described with reference to FIGS. 9 and 10,the lead-in area LI is positioned at the inside end points IA and IB ofeach track. Data for stabilizing the operation of the reproducingapparatus when reading starts is written to the lead-in area LI.

The lead-out area LO is correspondingly located at the outsidecircumference of the optical disk, i.e., at outside end points OA and OBof each track in the disks described with reference to FIGS. 9 and 10.Data identifying the end of the volume space VS is recorded in thislead-out area LO.

The volume space VS is located between the lead-in area LI and lead-outarea LO, and is recorded as a one-dimensional array of n+l (where n isan integer greater than or equal to zero) 2048-byte logic sectors LS.The logic sectors LS are sequentially number #0, #1, #2, . . . #n. Thevolume space VS is also divided into a volume and file structuremanagement area VFS and a file data structure area FDS.

The volume and file structure management area VFS comprises m+1 logicsectors LS#0 to LS#m (where m is an integer greater than or equal tozero and less than n. The file data structure FDS comprises n-m logicsectors LS #m+1 to LS #n.

Note that this file data structure area FDS corresponds to themultimedia bitstream MBS shown in FIG. 1 and described above.

The volume file structure VFS is the file system for managing the datastored to the volume space VS as files, and is divided into logicsectors LS#0-LS#m where m is the number of sectors required to store alldata needed to manage the entire disk, and is a natural number less thann. Information for the files stored to the file data structure area FDSis written to the volume file structure VFS according to a knownspecification such as IS0-9660 or IS0-13346.

The file data structure area FDS comprises n-m logic sectors LS#m-LS#n,each comprising a video manager VMG sized to an integer multiple of thelogic sector (2048×I, where I is a known integer), and k video titlesets VTS #1-VTS#k (where k is a natural number less than 100).

The video manager VMG stores the title management information for theentire disk, and information for building a volume menu used to set andchange reproduction control of the entire volume.

Any video title set VTS #k is also called a “video file” representing atitle comprising video, audio, and/or still image data.

The internal structure of each video title set VTS shown in FIG. 22 isshown in FIG. 16. Each video title set VTS comprises VTS informationVTSI describing the management information for the entire disk, and theVTS title video objects VOB (VTSTT_VOBS), i.e., the system stream of themultimedia bitstream. The VTS information VTSI is described first below,followed by the VTS title VOBS.

The VTS information primarily includes the VTSI management tableVTSI_MAT and VTSPGC information table VTS_PGCIT.

The VTSI management table VTSI_MAT stores such information as theinternal structure of the video title set VTS, the number of selectableaudio streams contained in the video title set VTS, the number ofsub-pictures, and the video title set VTS location (storage address).

The VTSPGC information table VTS_PGCIT records i (where i is a naturalnumber) program chain (PGC) data blocks VTS_PGCI #1-VTS_PGCI #i forcontrolling the playback sequence. Each of the table entries VTS_PGCI #iis a data entry expressing the program chain, and comprises j (where jis a natural number) cell playback information blocks C_PBI #1-C_PBI #j.Each cell playback information block C_PBI #j contains the playbacksequence of the cell and playback control information.

The program chain PGC is a conceptual structure describing the story ofthe title content, and therefore defines the structure of each title bydescribing the cell playback sequence. Note that these cells aredescribed in detail below.

If, for example, the video title set information relates to the menus,the video title set information VTSI is stored to a buffer in theplayback device when playback starts. If the user then presses a MENUbutton on a remote control device, for example, during playback, theplayback device references the buffer to fetch the menu information anddisplay the top menu #1. If the menus are hierarchical, the main menustored as program chain information VTS_PGCI #1 may be displayed, forexample, by pressing the MENU button, VTS_PGCI #2-#9 may correspond tosubmenus accessed using the numeric keypad on the remote control, andVTS_PGCI #10 and higher may correspond to additional submenus furtherdown the hierarchy. Alternatively, VTS_PGCI #1 may be the top menudisplayed by pressing the MENU button, while VTS_PGCI #2 and higher maybe voice guidance reproduced by pressing the corresponding numeric key.

The menus themselves are expressed by the plural program chains definedin this table. As a result, the menus may be freely constructed invarious ways, and shall not be limited to hierarchical ornon-hierarchical menus or menus containing voice guidance.

In the case of a movie, for example, the video title set informationVTSI is stored to a buffer in the playback device when playback starts,the playback device references the cell playback sequence described bythe program chain PGC, and reproduces the system stream.

The “cells” referenced here may be all or part of the system stream, andare used as access points during playback. Cells can therefore be used,for example, as the “chapters” into which a title may be divided.

Note that each of the PGC information entries C_PBI #j contain both cellplayback processing information and a cell information table. The cellplayback processing information comprises the processing informationneeded to reproduce the cell, such as the presentation time and numberof repetitions. More specifically, this information includes the cellblock mode CBM, cell block type CBT, seamless playback flag SPF,interleaved allocation flag IAF, STC resetting flag STCDF, cellpresentation time C_PBTM, seamless angle change flag SACF, first cellVOBU start address C_FVOBU_SA, and the last cell VOBU start addressC_LVOBU_SA.

Note that seamless playback refers to the reproduction in a digitalvideo disk system of multimedia data including video, audio, andsub-picture data without intermittent breaks in the data or information.Seamless playback is described in detail in another section below withreference to FIG. 23 and FIG. 24.

The cell block mode CBM indicates whether plural cells constitute onefunctional block. The cell playback information of each cell in afunctional block is arranged consecutively in the PGC information. Thecell block mode CBM of the first cell playback information in thissequence contains the value of the first cell in the block, and the cellblock mode CBM of the last cell playback information in this sequencecontains the value of the last cell in the block. The cell block modeCBM of each cell arrayed between these first and last cells contains avalue indicating that the cell is a cell between these first and lastcells in that block.

The cell block type CBT identifies the type of the block indicated bythe cell block mode CBM. For example, when a multiple angle function isenabled, the cell information corresponding to each of the reproducibleangles is programmed as one of the functional blocks mentioned above,and the type of these functional blocks is defined by a valueidentifying “angle” in the cell block type CBT for each cell in thatblock.

The seamless playback flag SPF simply indicates whether thecorresponding cell is to be linked and played back seamlessly with thecell or cell block reproduced immediately therebefore. To seamlesslyreproduce a given cell with the preceding cell or cell block, theseamless playback flag SPF is set to 1 in the cell playback informationfor that cell; otherwise SPF is set to 0.

The interleaved allocation flag IAF stores a value identifying whetherthe cell exists in a contiguous or interleaved block. If the cell ispart of an interleaved block, the flag IAF is set to 1; otherwise it isset to 0.

The STC resetting flag STCDF identifies whether the system time clockSTC used for synchronization must be reset when the cell is played back;when resetting the system time clock STC is necessary, the STC resettingflag STCDF is set to 1.

The seamless angle change flag SACF stores a value indicating whether acell in a multi-angle period should be connected seamlessly at an anglechange. If the angle change is seamless, the seamless angle change flagSACF is set to 1; otherwise it is set to 0.

The cell presentation time C_PBTM expresses the cell presentation timewith video frame precision.

The first cell VOBU start address C_FVOBU_SA is the VOBU start addressof the first cell in a block, and is also expressed as the distance fromthe logic sector of the first cell in the VTS title VOBS (VTSTT_VOBS) asmeasured by the number of sectors.

The last cell VOBU start address C_LVOBU_SA is the VOBU start address ofthe last cell in the block. The value of this address is expressed asthe distance from the logic sector of the first cell in the VTS titleVOBS (VTSTT_VOBS) as measured by the number of sectors.

The VTS title VOBS (VTSTT_VOBS), i.e., the multimedia system streamdata, is described next. The system stream data VTSTT_VOBS comprises i(where i is a natural number) system streams SS, each of which isreferred to as a “video object” (VOB). Each video object VOB #1-VOB #icomprises at least one video data block interleaved with up to a maximumeight audio data blocks and up to a maximum 32 sub-picture data blocks.

Each video object VOB comprises q (where q is a natural number) cellsC#1-C#q. Each cell C comprises r (where r is a natural number) videoobject units VOBU #1-VOBU #r.

Each video object unit VOBU comprises plural groups_of_pictures GOP, andthe audio and sub-pictures corresponding to the playback of said pluralgroups_of_pictures GOP. Note that the group_of_pictures GOP correspondsto the video encoding refresh cycle. Each video object unit VOBU alsostarts with an NV pack, i.e., the control data for that VOBU.

The structure of the navigation packs NV is described with reference toFIG. 18.

Before describing the navigation pack NV, the internal structure of thevideo zone VZ (see FIG. 22), i.e., the system stream St35 encoded by theauthoring encoder EC described with reference to FIG. 25, is describedwith reference to FIG. 17. Note that the encoded video stream St15 shownin FIG. 17 is the compressed one-dimensional video data stream encodedby the video encoder 300. The encoded audio stream St19 is likewise thecompressed one-dimensional audio data stream multiplexing the right andleft stereo audio channels encoded by the audio encoder 700. Note thatthe audio signal shall not be limited to a stereo signal, and may alsobe a multichannel surround-sound signal.

The system stream (title editing unit VOB) St35 is a one dimensionalarray of packs with a byte size corresponding to the logic sectors LS #nhaving a 2048-byte capacity as described using FIG. 21. A stream controlpack is placed at the beginning of the title editing unit (VOB) St35,i.e., at the beginning of the video object unit VOBU. This streamcontrol pack is called the “navigation pack NV”, and records the dataarrangement in the system stream and other control information.

The encoded video stream St15 and the encoded audio stream St19 arepacketized in byte units corresponding to the system stream packs. Thesepackets are shown in FIG. 17 as packets V1, V2, V3, V4 . . . and A1, A2,A3 . . . . As shown in FIG. 17, these packets are interleaved in theappropriate sequence as system stream St35, thus forming a packetstream, with consideration given to the decoder buffer size and the timerequired by the decoder to expand the video and audio data packets. Inthe example shown in FIG. 17, the packet stream is interleaved in thesequence V1, V2, A1, V3, V4, A2 . . . .

Note that the sequence shown in FIG. 17 interleaves one video data unitwith one audio data unit. Significantly increased recording/playbackcapacity, high speed recording/playback, and performance improvements inthe signal processing LSI enable the DVD system to record plural audiodata and plural sub-picture data (graphics data) to one video data unitin a single interleaved MPEG system stream, and thereby enable the userto select the specific audio data and sub-picture data to be reproducedduring playback. The structure of the system stream used in this type ofDVD system is shown in FIG. 18 and described below.

As in FIG. 17, the packetized encoded video stream St15 is shown in FIG.18 as V1, V2, V3, V4, . . . In this example, however, there is not justone encoded audio stream St19, but three encoded audio streams St19A,St19B, and St19C input as the source data. There are also two encodedsub-picture streams St17A and St17B input as the source data sub-picturestreams. These six compressed data streams, St15, St19A, St19B, St19C,St17A and St17B, are interleaved to a single system stream St35.

The video data is encoded according to the MPEG specification with thegroup_of_pictures GOP being the unit of compression. In general, eachgroup_of_pictures GOP contains 15 frames in the case of an NTSc signal,but the specific number of frames compressed to one GOP is variable. Thestream management pack, which describes the management data containing,for example, the relationship between interleaved data, is alsointerleaved at the GOP unit interval. Because the group_of_pictures GOPunit is based on the video data, changing the number of video frames perGOP unit changes the interval of the stream management packs. Thisinterval is expressed in terms of the presentation time on the digitalvideo disk within a range from 0.4 sec. to 1.0 sec. referenced to theGOP unit. If the presentation time of contiguous plural GOP units isless than 1 sec., the management data packs for the video data of theplural GOP units is interleaved to a single stream.

These management data packs are referred to as navigation packs NV inthe digital video disk system. The data from one navigation pack NV tothe packet immediately preceding the next navigation pack NV forms onevideo object unit VOBU. In general, one contiguous playback unit thatcan be defined as one scene is called a video object VOB, and each videoobject VOB contains plural video object units VOBU. Data sets of pluralvideo objects VOB form a VOB set (VOBS). Note that these data units werefirst used in the digital video disk.

When plural of these data streams are interleaved, the navigation packsNV defining the relationship between the interleaved packs must also beinterleaved at a defined unit known as the pack number unit. Eachgroup_of_pictures GOP is normally a unit containing approximately 0. 5sec. of video data, which is equivalent to the presentation timerequired for 12-15 frames, and one navigation pack NV is generallyinterleaved with the number of data packets required for thispresentation time.

The stream management information contained in the interleaved video,audio, and sub-picture data packets constituting the system stream isdescribed below with reference to FIG. 19 As shown in FIG. 19, the datacontained in the system stream is recorded in a format packed orpacketized according to the MPEG2 standard. The packet structure isessentially the same for video, audio, and sub-picture data. one pack inthe digital video disk system has a 2048 byte capacity as describedabove, and contains a pack header PKH and one packet PES; each packetPES contains a packet header PTH and data block.

The pack header PKH records the time at which that pack is to be sentfrom stream buffer 2400 to system decoder 2500 (see FIG. 26), i.e., thesystem clock reference SCR defining the reference time for synchronizedaudio-visual data playback. The MPEG standard assumes that the systemclock reference SCR is the reference clock for the entire decoderoperation. With such disk media as the digital video disk, however, timemanagement specific to individual disk players can be used, and areference clock for the decoder system is therefore separately provided.

The packet header PTH similarly contains a presentation time stamp PTSand a decoding time stamp DTS, both of which are placed in the packetbefore the access unit (the decoding unit). The presentation time stampPTS defines the time at which the video data or audio data contained inthe packet should be output as the playback output after being decoded,and the decoding time stamp DTS defines the time at which the videostream should be decoded. Note that the presentation time stamp PTSeffectively defines the display start timing of the access unit, and thedecoding time stamp DTS effectively defines the decoding start timing ofthe access unit. If the PTS and DTS are the same time, the DTS isomitted.

The packet header PTH also contains an 8-bit field called the stream IDidentifying the packet type, i.e., whether the packet is a video packetcontaining a video data stream, a private packet, or an MPEG audiopacket.

Private packets under the MPEG2 standard are data packets of which thecontent can be freely defined. Private packet 1 in this embodiment ofthe invention is used to carry audio data other than the MPEG audiodata, and sub-picture data; private packet 2 carries the PCI packet andDSI packet.

Private packets 1 and 2 each comprise a packet header, private dataarea, and data area. The private data area contains an 8-bit sub-streamID indicating whether the recorded data is audio data or sub-picturedata. The audio data defined by private packet 2 may be defined as anyof eight types #0-#7 of linear PCM or AC-3 encoded data. Sub-picturedata may be defined as one of up to 32 types #0-#31.

The data area is the field to which data compressed according to theMPEG2 specification is written if the stored data is video data; linearPCM, AC-3, or MPEG encoded data is written if audio data is stored; orgraphics data compressed by runlength coding is written if sub-picturedata is stored.

MPEG2-compressed video data may be compressed by constant bit rate (CBR)or variable bit rate (VBR) coding. With constant bit rate coding, thevideo stream is input continuously to the video buffer at a constantrate. This contrasts with variable bit rate coding in which the videostream is input intermittently to the video buffer, thereby making itpossible to suppress the generation of unnecessary code. Both constantbit rate and variable bit rate coding can be used in the digital videodisk system.

Because MPEG video data is compressed with variable length coding, thedata quantity in each group_of_pictures GOP is not constant. The videoand audio decoding times also differ, and the time-base relationshipbetween the video and audio data read from an optical disk, and thetime-base relationship between the video and audio data output from thedecoder, do not match. The method of time-base synchronizing the videoand audio data is therefore described in detail below with reference toFIG. 26, but is described briefly below based on constant bit ratecoding.

The navigation pack NV structure is shown in FIG. 20. Each navigationpack NV starts with a pack header PKH, and contains a PCI packet and DSIpacket.

As described above, the pack header PKH records the time at which thatpack is to be sent from stream buffer 2400 to system decoder 2500 (seeFIG. 26 ), i.e., the system clock reference SCR defining the referencetime for synchronized audio-visual data playback.

Each PCI packet contains PCI General Information (PCI_GI) and AngleInformation for Non-seamless playback (NMSL_AGLI).

The PCI General Information (PCI_GI) declares the display time of thefirst video frame (the Start PTM of VOBU (VOBU_S_PTM)), and the displaytime of the last video frame (End PTM of VOBU (VOBU_E_PTM)), in thecorresponding video object unit VOBU with system clock precision (90Khz).

The Angle Information for Non-seamless playback (NMSL_AGLI) states theread start address of the corresponding video object unit VOBU when theangle is changed expressed as the number of sectors from the beginningof the video object VOB. Because there are nine or fewer angles in thisexample, there are nine angle address declaration cells: DestinationAddress of Angle Cell #1 for Non-seamless playback (NMSL_AGL_Cl_DSTA) toDestination Address of Angle Cell #9 for Non-seamless playback(NMSL_AGL_C9_DSTA).

Each DSI packet contains DSI General Information (DSI_GI), SeamlessPlayback Information (SML_PBI), and Angle Information for Seamlessplayback (SML_AGLI).

The DSI General Information (DSI_GI) declares the address of the lastpack in the video object unit VOBU, i. e., the End Address for VOB(VOBU_EA), expressed as the number of sectors from the beginning of thevideo object unit VOBU.

While seamless playback is described in detail later, it should be notedthat the continuously read data units must be interleaved (multiplexed)at the system stream level as an interleaved unit ILVU in order toseamlessly reproduce split or combined titles. Plural system streamsinterleaved with the interleaved unit ILVU as the smallest unit aredefined as an interleaved block.

The Seamless Playback Information (SML_PBI) is declared to seamlesslyreproduce the stream interleaved with the interleaved unit ILVU as thesmallest data unit, and contains an Interleaved Unit Flag (ILVU flag)identifying whether the corresponding video object unit VOBU is aninterleaved block. The ILVU flag indicates whether the video object unitVOBU is in an interleaved block, and is set to 1 when it is. Otherwisethe ILVU flag is set to 0.

When a video object unit VOBU is in an interleaved block, a Unit ENDflag is declared to indicate whether the video object unit VOBU is thelast VOBU in the interleaved unit ILVU. Because the interleaved unitILVU is the data unit for continuous reading, the Unit END flag is setto 1 if the VOBU currently being read is the last VOBU in theinterleaved unit ILVU. Otherwise the Unit END flag is set to 0.

An Interleaved Unit End Address (ILVU_EA) identifying the address of thelast pack in the ILVU to which the VOBU belongs, and the startingaddress of the next interleaved unit ILVU, Next Interleaved Unit StartAddress (NT_ILVU_SA), are also declared when a video object unit VOBU isin an interleaved block. Both the Interleaved Unit End Address (ILVU_EA)and Next Interleaved Unit Start Address (NT_ILVU_SA) are expressed asthe number of sectors from the navigation pack NV of that VOBU.

When two system streams are seamlessly connected but the audiocomponents of the two system streams are not contiguous, particularlyimmediately before and after the seam, it is necessary to pause theaudio output to synchronize the audio and video components of the systemstream following the seam. Note that non-contiguous audio may resultfrom different audio signals being recording with the correspondingvideo blocks. With an NTSC signal, for example, the video frame cycle isapproximately 33. 33 msec while the AC-3 audio frame cycle is 32 msec.

To enable this resynchronization, audio reproduction stopping times 1and 2, i.e., Audio Stop PTM 1 in VOB (VOB_A_STP_PTM1), and Audio StopPTM2 in VOB (VOB_A_STP_PTM2), indicating the time at which the audio isto be paused; and audio reproduction stopping periods 1 and 2, i.e.,Audio Gap Length 1 in VOlB (VOB_A_GAP_LEN1) and Audio Gap Length 2 inVOB (VOB_A GAP_LEN2), indicating for how long the audio is to be paused,are also declared in the DSI packet. Note that these times are specifiedat the system clock precision (90 Khz).

The Angle Information for Seamless playback (SML_AGLI) declares the readstart address when the angle is changed. Note that this field is; validwhen seamless, multi-angle control is enabled. This address is alsoexpressed as the number of sectors from the navigation pack NV of thatVOBU. Because there are nine or fewer angles, there are nine angleaddress declaration cells: Destination Address of Angle Cell #1 forSeamless playback (SML_AGL_Cl_DSTA) to Destination Address of Angle Cell#9 for Seamless playback (SML_AGL_C9_DSTA).

Note also that each title is edited in video object (VOB) units.Interleaved video objects (interleaved title editing units) arereferenced as “VOBS”; and the encoded range of the source data is theencoding unit.

DVD Encoder

A preferred embodiment of a digital video disk system authoring encoderECD in which the multimedia bitstream authoring system according to thepresent invention is applied to a digital video disk system is describedbelow and shown in FIG. 25 it will be obvious that the authoring encoderECD applied to the digital video disk system, referred to below as a DVDencoder, is substantially identical to the authoring encoder EC shown inFIG. 2. The basic difference between these encoders is the replacementin the DVD encoder ECD of the video zone formatter 1300 of the authoringencoder EC above with a VOB buffer 1000 and formatter 1100. It will alsobe obvious that the bitstream encoded by this DVD encoder ECD isrecorded to a digital video disk medium M. The operation of this DVDencoder ECD is therefore described below in comparison with theauthoring encoder EC described above.

As in the above authoring encoder EC, the encoding system controller 200generates control signals St9, St11, St13, St21, St23, St25, St33, andSt39 based on the scenario data St7 describing the user-defined editinginstructions input from the scenario editor 100, and controls the videoencoder 300, sub-picture encoder 500, and audio encoder 700 in the DVDencoder ECD. Note that the user-defined editing instructions in the DVDencoder ECD are a superset of the editing instructions of the authoringencoder EC described above.

Specifically, the user-defined editing instructions (scenario data St7)in the DVD encoder ECD similarly describe what source data is selectedfrom all or a subset of the source data containing plural titles withina defined time period, and how the selected source data is reassembledto reproduce the scenario (sequence) intended by the user. The scenariodata St7 of the DVD encoder ECD, however, further contains suchinformation as: the number of streams contained in the editing units,which are obtained by splitting a multi-title source stream into blocksat a constant time interval; the number of audio and sub-picture datacells contained in each stream, and the sub-picture display time andperiod; whether the title is a multi-rated title enabling parental lockcontrol; whether the user content is selected from plural streamsincluding, for example, multiple viewing angles; and the method ofconnecting scenes when the angle is switched among the multiple viewingangles.

The scenario data St7 of the DVD encoder ECD also contains controlinformation on a video object VOB unit basis. This information isrequired to encode the media source stream, and specifically includessuch information as whether there are multiple angles or parentalcontrol features. When multiple angle viewing is enabled, the scenariodata St7 also contains the encoding bit rate of each stream consideringdata interleaving and the disk capacity, the start and end times of eachcontrol, and whether a seamless connection should be made between thepreceding and following streams.

The encoding system controller 200 extracts this information from thescenario data St7, and generates the encoding information table andencoding parameters required for encoding control. The encodinginformation table and encoding parameters are described with referenceto FIGS. 27, 28, and 29 below.

The stream encoding data St33 contains the system stream encodingparameters and system encoding start and end timing values required bythe DVD system to generate the VOBS. These system stream encodingparameters include the conditions for connecting one video object VOBwith those before and after, the number of audio streams, the audioencoding information and audio Ids, the number of sub-pictures and thesub-picture Ids, the video playback starting time information VPTS, andthe audio playback starting time information APTS.

The title sequence control signal St39 supplies the multimedia bitstreamMBS formatting start and end timing information and formattingparameters declaring the reproduction control information and interleaveinformation.

Based on the video encoding parameter and encoding start/end timingsignal St9, the video encoder 300 encodes a specific part of the videostream St1 to generate an elementary stream conforming to the MPEG2Video standard defined in ISO-13818. This elementary stream is output tothe video stream buffer 400 as encoded video stream St15.

Note that while the video encoder 300 generates an elementary streamconforming to the MPEG2 Video standard defined in IS0-13818, specificencoding parameters are input via the video encoding parameter signalSt9, including the encoding start and end timing, bit rate, the encodingconditions for the encoding start and end, the material type, includingwhether the material is an NTSC or PAL video signal or telecineconverted material, and whether the encoding mode is set for either openGOP or closed GOP encoding.

The MPEG2 coding method is basically an interframe coding method usingthe correlation between frames for maximum signal compression, i.e., theframe being coded (the target frame) is coded by referencing framesbefore and/or after the target frame. However, intra-coded frames, i.e., frames that are coded based solely on the content of the targetframe, are also inserted to avoid error propagation and enableaccessibility from mid-stream (random access). The coding unitcontaining at least one intra-coded frame (“intra-frame”) is called agroup_of_pictures GOP.

A group_of_pictures GOP in which coding is closed completely within thatGOP is known as a “closed GOP. ” A group_of_pictures GOP containing aframe coded with reference to a frame in a preceding or following(IS0-13818 DOES NOT LIMIT P- and B-picture CODING to referencing PASTframes) group_of_pictures GOP is an “open GOP.” It is therefore possibleto playback a closed GOP using only that GOP. Reproducing an open GOP,however, also requires the presence of the referenced GOP, generally theGOP preceding the open GOP.

The GOP is often used as the access unit. For example, the GOP may beused as the playback start point for reproducing a title from themiddle, as a transition point in a movie, or for fast-forward play andother special reproduction modes. High speed reproduction can beachieved in such cases by reproducing only the intra-frame coded framesin a GOP or by reproducing only frames in GOP units.

Based on the sub-picture stream encoding parameter signal St11, thesub-picture encoder 500 encodes a specific part of the sub-picturestream St3 to generate a variable length coded bitstream of bitmappeddata. This variable length coded bitstream data is output as the encodedsub-picture stream St17 to the sub-picture stream buffer 600.

Based on the audio encoding parameter signal St13, the audio encoder 700encodes a specific part of the audio stream St5 to generate the encodedaudio data. This encoded audio data may be data based on the MPEG1 audiostandard defined in IS0-11172 and the MPEG2 audio standard defined inISO-13818, AC-3 audio data, or PCM (LPCM) data. Note that the methodsand means of encoding audio data according to these standards are knownand commonly available.

The video stream buffer 400 is connected to the video encoder 300 and tothe encoding system controller 200. The video stream buffer 400 storesthe encoded video stream St15 input from the video encoder 300, andoutputs the stored encoded video stream St15 as the time-delayed encodedvideo stream St27 based on the timing signal St21 supplied from theencoding system controller 200.

The sub-picture stream buffer 600 is similarly connected to thesub-picture encoder 500 and to the encoding system controller 200. Thesub-picture stream buffer 600 stores the encoded sub-picture stream St17input from the sub-picture encoder 500, and then outputs the storedencoded sub-picture stream St17 as time-delayed encoded sub-picturestream St29 based on the timing signal St23 supplied from the encodingsystem controller 200.

The audio stream buffer 800 is similarly connected to the audio encoder700 and to the encoding system controller 200. The audio stream buffer800 stores the encoded audio stream St19 input from the audio encoder700, and then outputs the encoded audio stream St19 as the time-delayedencoded audio stream St31 based on the timing signal St25 supplied fromthe encoding system controller 200.

The system encoder 900 is connected to the video stream buffer 400,sub-picture stream buffer 600, audio stream buffer 800, and the encodingsystem controller 200, and is respectively supplied thereby with thetime-delayed encoded video stream St27, time-delayed encoded sub-picturestream St29, time-delayed encoded audio stream St31, and the systemstream encoding parameter data St33. Note that the system encoder 900 isa multiplexer that multiplexes the time-delayed streams St27, St29, andSt31 based on the stream encoding data St33 (timing signal) to generatetitle editing units (VOBs) St35.

The VOB buffer 1000 temporarily stores the video objects VOBs producedby the system encoder 900. The formatter 1100 reads the delayed videoobjects VOB from the VOB buffer 1000 based on the title sequence controlsignal St39 to generate one video zone VZ, and adds the volume filestructure VFS to generate the edited multimedia stream data St43.

The multimedia bitstream MBS St43 edited according to the user-definedscenario is then sent to the recorder 1200. The recorder 1200 processesthe edited multimedia stream data St43 to the data stream St45 format ofthe recording medium M, and thus records the formatted data stream St45to the recording medium M.

DVD Decoder

A preferred embodiment of a digital video disk system authoring decoderDCD in which the multimedia bitstream authoring system of the presentinvention is applied to a digital video disk system is described belowand shown in FIG. 26. The authoring decoder DCD applied to the digitalvideo disk system, referred to below as a DVD decoder DCD, decodes themultimedia bitstream MBS edited using the DVD encoder ECD of the presentinvention, and recreates the content of each title according to theuser-defined scenario. It will also be obvious that the multimediabitstream St45 encoded by this DVD encoder ECD is recorded to a digitalvideo disk medium M.

The basic configuration of the DVD decoder DCD according to thisembodiment is the same as that of the authoring decoder DC shown in FIG.3. The differences are that a different video decoder 3801 (shown as3800 in FIG. 26) is used in place of the video decoder 3800, and areordering buffer 3300 and selector 3400 are disposed between the videodecoder 3801 and synthesizer 3500.

Note that the selector 3400 is connected to the synchronizer 2900, andis controlled by a switching signal St103.

The operation of this DVD decoder DCD is therefore described below incomparison with the authoring decoder DC described above.

As shown in FIG. 26, the DVD decoder DCD comprises a multimediabitstream producer 2000, scenario selector 2100, decoding systemcontroller 2300, stream buffer 2400, system decoder 2500, video buffer2600, sub-picture buffer 2700, audio buffer 2800, synchronizer 2900,video decoder 3801, reordering buffer 3300, sub-picture decoder 3100,audio decoder 3200, selector 3400, synthesizer 3500, video data outputterminal 3600, and audio data output terminal 3700.

The bitstream producer 2000 comprises a recording media drive unit 2004for driving the recording medium M; a reading head 2006 for reading theinformation recorded to the recording medium M and producing the binaryread signal St57; a signal processor 2008 for variously processing theread signal St57 to generate the reproduced bitstream St61; and areproduction controller 2002.

The reproduction controller 2002 is connected to the decoding systemcontroller 2300 from which the multimedia bitstream reproduction controlsignal St53 is supplied, and in turn generates the reproduction controlsignals St55 and St59 respectively controlling the recording media driveunit (motor) 2004 and signal processor 2008.

So that the user-defined video, sub-picture, and audio portions of themultimedia title edited by the authoring encoder EC are reproduced, theauthoring decoder DC comprises a scenario selector 2100 for selectingand reproducing the corresponding scenes (titles). The scenario selector2100 then outputs the selected titles as scenario data to the DVDdecoder DCD.

The scenario selector 2100 preferably comprises a keyboard, CPU, andmonitor. Using the keyboard, the user then inputs the desired scenariobased on the content of the scenario input by the DVD encoder ECD. Basedon the keyboard input, the CPU generates the scenario selection dataSt51 specifying the selected scenario. The scenario selector 2100 isconnected to the decoding system controller 2300 by an infraredcommunications device, for example, and inputs the generated scenarioselection data St51 to the decoding system controller 2300.

The stream buffer 2400 has a specific buffer capacity used totemporarily store the reproduced bitstream St61 input from the bitstreamproducer 2000, extract the volume file structure VFS, the initialsynchronization data SCR (system clock reference) in each pack, and theVOBU control information (DSI) in the navigation pack NV, to generatethe bitstream control data St63. The stream buffer 2400 is alsoconnected to the decoding system controller 2300, to which it suppliesthe generated bitstream control data St63.

Based on the scenario selection data St51 supplied by the scenarioselector 23.00, the decoding system controller 2300 then generates thebitstream reproduction control signal St53 controlling the operation ofthe bitstream producer 2000. The decoding system controller 2300 alsoextracts the user-defined playback instruction data from the bitstreamreproduction control signal St53, and generates the decoding informationtable required for decoding control. This decoding information table isdescribed further below with reference to FIGS. 26 and 32. The decodingsystem controller 2300 also extracts the title information recorded tothe optical disk M from the file data structure area FDS of thebitstream control data St63 to generate the title information signalSt200. Note that the extracted title information includes the videomanager VMG, VTS information VTSI, the PGC information entries C_PBI #j,and the cell presentation time C_PBTM.

Note that the bitstream control data St63 is generated in pack units asshown in FIG. 19, and is supplied from the stream buffer 2400 to thedecoding system controller 2300, to which the stream buffer 2400 isconnected.

The synchronizer 2900 is connected to the decoding system controller2300 from which it receives the system clock reference SCR contained inthe synchronization control data St81 to set the internal system clockSTC and supply the reset system clock St79 to the decoding systemcontroller 2300.

Based on this system clocks St79, the decoding system controller 2300also generates the stream read signal St65 at a specific interval andoutputs the read signal St65 to the stream buffer 2400. Note that theread unit in this case is the pack.

The method of generating the stream read signal St65 is described next.

The decoding system controller 2300 compares the system clock referenceSCR contained in the stream control data extracted from the streambuffer 2400 with the system clock St79 supplied from the synchronizer2900, and generates the read request signal St65 when the system clockSt79 is greater than the system clock reference SCR of the bitstreamcontrol data St63. Pack transfers are controlled by executing thiscontrol process on a pack unit.

Based on the scenario selection data St51, the decoding systemcontroller 2300 generates the decoding signal St69 defining the streamIds for the video, sub-picture, and audio bitstreams corresponding tothe selected scenario, and outputs to the system decoder 2500.

When a title contains plural audio tracks, e.g. audio tracks inJapanese, English, French, and/or other languages, and pluralsub-picture tracks for subtitles in Japanese, English, French, and/orother languages, for example, a discrete ID is assigned to each of thelanguage tracks. As described above with reference to FIG. 19, a streamID is assigned to the video data and MPEG audio data, and a substream IDis assigned to the sub-picture data, AC-3 audio data, linear PCM data,and navigation pack NV information. While the user need never be awareof these ID numbers, the user can select the language of the audioand/or subtitles using the scenario selector 2100. If English languageaudio is selected, for example, the ID corresponding to the Englishaudio track is sent to the decoding system controller 2300 as scenarioselection data St51. The decoding system controller 2300 then adds thisID to the decoding signal St69 output to the system decoder 2500.

Based on the instructions contained in the decoding signal St69, thesystem decoder 2500 respectively outputs the video, sub-picture, andaudio bitstreams input from the stream buffer 2400 to the video buffer2600, sub-picture buffer 2700, and audio buffer 2800 as the encodedvideo stream St71, encoded sub-picture stream St73, and encoded audiostream St75. Thus, when the stream ID input from the scenario selector2100 and the pack ID input from the stream buffer 2400 match, the systemdecoder 2500 outputs the corresponding packs to the respective buffers(i.e., the video buffer 2600, sub-picture buffer 2700, and audio buffer2800).

The system decoder 2500 detects the presentation time stamp PTS anddecoding time stamp DTS of the smallest control unit in each bitstreamSt67 to generate the time information signal St77. This time informationsignal St77 is supplied to the synchronizer 2900 through the decodingsystem controller 2300 as the synchronization control data St81.

Based on this synchronization control data St81, the synchronizer 2900determines the decoding start timing whereby each of the bitstreams willbe arranged in the correct sequence after decoding, and then generatesand inputs the video stream decoding start signal St89 to the videodecoder 3801 based on this decoding timing. The synchronizer 2900 alsogenerates and supplies the sub-picture decoding start signal St91 andaudio stream decoding start signal St93 to the sub-picture decoder 3100and audio decoder 3200, respectively.

The video decoder 3801 generates the video output request signal St84based on the video stream decoding start signal St89, and outputs to thevideo buffer 2600. In response to the video output request signal St84,the video buffer 2600 outputs the video stream St83 to the video decoder3801. The video decoder 3801 thus detects the presentation timeinformation contained in the video stream St83, and disables the videooutput request signal St84 when the length of the received video streamSt83 is equivalent to the specified presentation time. A video streamequal in length to the specified presentation time is thus decoded bythe video decoder 3801, which outputs the reproduced video signal St95to the reordering buffer 3300 and selector 3400.

Because the encoded video stream is coded using the interframecorrelations between pictures, the coded order and display order do notnecessarily match on a frame unit basis. The video cannot, therefore, bedisplayed in the decoded order. The decoded frames are thereforetemporarily stored to the reordering buffer 3300. The synchronizer 2900therefore controls the switching signal St103 so that the reproducedvideo signal St95 output from the video decoder 3800 and the reorderingbuffer output St97 are appropriately selected and output in the displayorder to the synthesizer 3500.

The sub-picture decoder 3100 similarly generates the sub-picture outputrequest signal St86 based on the sub-picture decoding start signal St91,and outputs to the sub-picture buffer 2700. In response to thesub-picture output request signal St86, the sub-picture buffer 2700outputs the sub-picture stream St85 to the sub-picture decoder 3100.Based on the presentation time information contained in the sub-picturestream St85, the sub-picture decoder 3100 decodes a length of thesub-picture stream St85 corresponding to the specified presentation timeto reproduce and supply to the synthesizer 3500 the sub-picture signalSt99.

The synthesizer 3500 superimposes the selector 3400 output with thesub-picture signal St99 to generate and output the video signal St105 tothe video data output terminal 3600.

The audio decoder 3200 generates and supplies to the audio buffer 2800the audio output request signal St88 based on the audio stream decodingstart signal St93. The audio buffer 2800 thus outputs the audio streamSt87 to the audio decoder 3200. The audio decoder 3200 decodes a lengthof the audio stream St87 corresponding to the specified presentationtime based on the presentation time information contained in the audiostream St87, and outputs the decoded audio stream St101 to the audiodata output terminal 3700.

It is thus possible to reproduce a user-defined multimedia bitstream MBSin real-time according to a user-defined scenario. More specifically,each time the user selects a different scenario, the DVD decoder DCD isable to reproduce the title content desired by the user in the desiredsequence by reproducing the multimedia bitstream MBS corresponding tothe selected scenario.

It should be noted that the decoding system controller 2300 may supplythe title information signal St200 to the scenario selector 2100 bymeans of the infrared communications device mentioned above or anothermeans. Interactive scenario selection controlled by the user can also bemade possible by the scenario selector 2100 extracting the titleinformation recorded to the optical disk M from the file data structurearea FDS of the bitstream control data St63 contained in the titleinformation signal St200, and displaying this title information on adisplay for user selection.

Note, further, that the stream buffer 2400, video buffer 2600,sub-picture buffer 2700, audio buffer 2800, and reordering buffer 3300are expressed above and in the figures as separate entities because theyare functionally different. It will be obvious, however, that a singlebuffer memory can be controlled to provide the same discretefunctionality by time-share controlled use of a buffer memory with anoperating speed plural times faster than the read and write rates ofthese separate buffers.

Multi-scene control

The concept of multiple angle scene control according to the presentinvention is described below with reference to FIG. 21. As describedabove, titles that can be played back with numerous variations areconstructed from basic scene periods containing data common to eachtitle, and multi-scene periods comprising groups of different scenescorresponding to the various scenario requests. In FIG. 21, scenes 1, 5,and 8 are the common scenes of the basic scene periods. The multi-anglescenes (angles 1, 2, and 3) between scenes 1 and 5, and the parentallocked scenes (scenes 6 and 7) between scenes 5 and 8, are themulti-scene periods.

Scenes taken from different angles, i.e., angles 1, 2, and 3 in thisexample, can be dynamically selected and reproduced during playback inthe multi-angle scene period. In the parental locked scene period,however, only one of the available scenes, scenes 6 and.7, havingdifferent content can be selected, and must be selected staticallybefore playback begins.

Which of these scenes from the multi-scene periods is to be selected andreproduced is defined by the user operating the scenario selector 2100and thereby generating the scenario selection data St51. In scenario 1in FIG. 21 the user can freely select any of the multi-angle scenes, andscene 6 has been preselected for output in the parental locked sceneperiod. Similarly in scenario 2, the user can freely select any of themulti-angle scenes, and scene 7 has been preselected for output in theparental locked scene period.

With reference to FIGS. 30 and 31, furthermore, the contents of theprogram chain information VTS_PGCI is described. In FIG. 30, the casethat a scenario requested by the user is shown with respect to a VTSIdata construction. The scenario 1 and scenario 2 shown in FIG. 21 aredescribed as program chain information VTS_PGC#1 and VTS_PGC#2.VTS_PGC#l describing the scenario 1 consists of cell playbackinformation C_PBI#1 corresponding to scene 1, C_PBI#2, C_PBI#3, andC_PBI#4 within a multi-angle cell block, C_PBI#5 corresponding to scene5, C_PBI#6 corresponding to scene 6, and C_PBI#7 corresponding to scene8.

VTS_PGCI#2 describing the scenario 2 consists of cell playbackinformation C_PBI#1 corresponding to scene 1, C_PBI#2, C_PBI#3, andC_PBI#4 within a multi-angle cell block corresponding to a multi-anglescene, C_PBI#5 corresponding to scene 5, C_PBI#6 corresponding to scene7, and C_PBI#7 corresponding to scene 8. According to the digital videosystem data structure, a scene which is a control unit of a scenario isdescribed as a cell which is a unit thereunder, thus a scenariorequested by a user can be obtained.

In FIG. 31, the case that a scenario requested by the user shown in FIG.21 is shown with respect to a VOB data construction VTSTT_VOBS. Asspecifically shown in FIG. 31, the two scenarios 1 and 2 use the sameVOB data in common. With respect to a single scene commonly owned byeach scenario, VOB#1 corresponding to scene 1, VOB#5 corresponding toscene 5, and VOB#8 corresponding to scene 8 are arranged innon-interleaved block which is the contiguous block.

With respect to the multi-angle data commonly owned by scenarios 1 and2, one angle scene data is constructed by a single VOB. Specificallyspeaking, angle 1 is constructed by VOB#2, and angle 2 is constructed byVOB#3, angle 3 is constructed by VOB#4. Thus constructed multi-angledata is formed as the interleaved block for the sake of switchingbetween each angle and seamless reproduction of each angle data. Scenes6 and 7 peculiar to scenarios 1 and 2, respectively, are formed as theinterleaved block for the sake of seamless reproduction between commonscenes before and behind thereof as well as seamless reproductionbetween each scene.

As described in the above, the user's requesting scenario shown in FIG.21 can be realized by utilizing the video title playback controlinformation shown in FIG. 30 and the title playback VOB data structureshown in FIG. 31.

Seamless Playback

The seamless playback capability briefly mentioned above with regard tothe digital video disk system data structure is described below. Notethat seamless playback refers to the reproduction in a digital videodisk system of multimedia data including video, audio, and sub-picturedata without intermittent breaks in the data or information betweenbasic scene periods, between basic scene periods and multi-sceneperiods, and between multi-scene periods.

Hardware factors contributing to intermittent playback of this data andtitle content include decoder underflow, i.e., an imbalance between thesource data input speed and the decoding speed of the input source data.

Other factors relate to the properties of the playback data. When theplayback data is data that must be continuously reproduced for aconstant time unit in order for the user to understand the content orinformation, e.g., audio data, data continuity is lost when the requiredcontinuous presentation time cannot be assured. Reproduction of suchinformation whereby the required continuity is assured is referred to as“contiguous information reproduction,” or “seamless informationreproduction.” Reproduction of this information when the requiredcontinuity cannot be assured is referred to as “non-continuousinformation reproduction,” or “non-seamless information reproduction.”It is obvious that continuous information reproduction andnon-continuous information reproduction are, respectively, seamless andnon-seamless reproduction.

Note that seamless reproduction can be further categorized as seamlessdata reproduction and seamless information reproduction. Seamless datareproduction is defined as preventing physical blanks or interruptionsin the data playback (intermittent reproduction) as a result of a bufferunderflow state, for example. Seamless information reproduction isdefined as preventing apparent interruptions in the information whenperceived by the user (intermittent presentation) when recognizinginformation from the playback data where there are no actual physicalbreaks in the data reproduction. The specific method enabling seamlessreproduction as thus described is described later below with referenceto FIGS. 23 and 24.

Interleaving

The DVD data system streams described above are recorded using anappropriate authoring encoder EC as a movie or other multimedia title ona DVD recording medium. Note that the following description refers to amovie as the multimedia title being processed, but it will be obviousthat the invention shall not be so limited.

Supplying a single movie in a format enabling the movie to be used inplural different cultural regions or countries requires the script to berecorded in the various languages used in those regions or countries. Itmay even necessitate editing the content to conform to the mores andmoral expectations of different cultures. Even using such alarge-capacity storage system as the DVD system, however, it isnecessary to reduce the bit rate, and therefore the image quality, ifplural full-length titles edited from a single common source title arerecorded to a single disk. This problem can be solved by recording thecommon parts of plural titles only once, and recording the segmentsdifferent in each title for each different title only. This method makesit possible to record plural titles for different countries or culturesto a single optical disk without reducing the bit rate, and, therefore,retaining high image quality.

As shown in FIG. 21, the titles recorded to a single optical diskcontain basic scene periods of scenes common to all scenarios, andmulti-scene periods containing scenes specific to certain scenarios, toprovide parental lock control and multi-angle scene control functions.

In the case of the parental lock control function, titles containing sexscenes, violent scenes, or other scenes deemed unsuitable for children,i.e., so-called “adult scenes,” are recorded with a combination ofcommon scenes, adult scenes, and children's scenes. These title streamsare achieved by arraying the adult and children's scenes to multi-sceneperiods between the common basic scene periods.

Multi-angle control can be achieved in a conventional single-angle titleby recording plural multimedia scenes obtained by recording the subjectsfrom the desired plural camera angles to the multi-scene periods arrayedbetween the common basic scene periods. Note, however, that while theseplural scenes are described here as scenes recorded from differentcamera angles (positions), it will be obvious that the scenes may berecorded from the same camera angle but at different times, datagenerated by computer graphics, or other video data.

When data is shared between different scenarios of a single title, it isobviously necessary to move the laser beam LS from the common scene datato the non-common scene data during reproduction, i.e., to move theoptical pickup to a different position on the DVD recording medium RC1.The problem here is that the time required to move the optical pickupmakes it difficult to continue reproduction without creating breaks inthe audio or video, i.e., to sustain seamless reproduction. This problemcan be theoretically solved by providing a track buffer (stream buffer2400) to delay data output an amount equivalent to the worst accesstime. In general, data recorded to an optical disk is read by theoptical pickup, appropriately processed, and temporarily stored to thetrack buffer. The stored data is subsequently decoded and reproduced asvideo or audio data.

The operation of the stream buffer 2400, or a track buffer, in this DVDsystem is described briefly below.

Because rotational speed control of the optical disk drive cannotinstantaneously adjust the disk speed, the input to the stream buffer2400, i.e., the transfer rate Vr from the optical disk, is a basicallyconstant rate. Output from the track buffer, i.e., the transfer rate Voto the decoder, however, varies according to the image quality, userintent, and even the variable bit rate of the compressed video data inthe DVD system. The from-disk transfer rate Vr is therefore constant atapproximately 11 Mbps in the DVD system, while the transfer rate Vo fromthe buffer is variable to a maximum 10 Mbps.

Because of this gap between the input and output transfer rates Vr andVo, the stream buffer 2400 will overflow if data is transferredcontinuously from disk. Therefore, to prevent the stream buffer 2400 ofthe reproduction apparatus overflowing, data is transferredintermittently from the disk. The stream buffer is controlled duringnormal continuous reproduction to always be in a near-overflow state.

It is therefore possible by using a stream buffer 2400 to sustaincontinuous, uninterrupted data output (reproduction) even if there is aslight break in data reading as a result of the read head (opticalpickup) 2006 jumping to move between logic sectors LS on the disk. In anactual reproduction apparatus, however, the jump time may vary between200 msec and 2 sec depending upon the distance and position on the diskM. While it is possible to use a stream buffer 2400 with capacitysufficient to absorb this jump time, the compression bit rate is anaverage 4-5 Mbps and a maximum 10 Mbps when using a large-capacityoptical disk M storing high quality images. Assuring seamlessreproduction when jumping from any disk position to any other with thissystem imposes significant memory requirements, resulting in anexpensive decoder DC. Because the amount of memory that can be built into the decoder DC is therefore limited if a cost-effective product is tobe marketed, other limitations are imposed, e. g., limiting the jumptime to a time whereby data can be continuously reproduced.

The relationship between the accumulated data quantity in the streambuffer 2400 and the operating mode of the reading head 2006 is shown inFIG. 32. In FIG. 32, period Tr is the period during which the opticalpickup reads data from the optical disk RC, and period Tj is the jumpperiod during which the optical pickup moves between logic sectors. LineL1 expresses the change in data volume Vd stored in the stream buffer2400 during the data read period Tr. Line L2 expresses the change indata volume Vd stored in the stream buffer 2400 during the jump periodTj.

During the data read period Tr, the reading head 2006 reads data fromthe optical disk M at the transfer rate Vr, and stores the read datadirectly to the stream buffer 2400. The stream buffer 2400 supplies thedata to the decoders 3801, 3100, and :3200 at the transfer rate Vo. As aresult, data accumulates in the stream buffer 2400 during the data readperiod Tr at the rate Vr−Vo, i.e., the difference between these twotransfer rates.

Because the reading head 2006 is moving to access a different diskposition during the jump period Tj, data read from the optical disk Mcannot be stored to the stream buffer 2400. Data continues to be outputfrom the stream buffer 2400 to the decoders 3801, 3100, and 3200 duringthis period, however, and the accumulated data volume Vd remaining inthe stream buffer 2400 decreases at the rate at which data istransferred to the) decoders, i.e., transfer rate Vo.

Note that while the transfer rate Vo to the decoders is shown in FIG. 32as a constant rate, data transfers to the decoders actually occurintermittently because the decoding time varies according to the datatype. These differences are omitted to simply this description of thebuffer underflow concept. This is equivalent to the reading head 2006reading data intermittently during the jump period Tj, even through thereading head 2006 continuously reads from the optical disk M at aconstant linear velocity (CLV). The slopes Li and L2 of lines L1 and L2above can be expressed by the following equations.

L1=Vr−Vo  [1]

L2=Vo  [2]

Underflow occurs, and decoding stops, when the jump period Tj is longenough for stream buffer 2400 to empty. If the jump period Tj is held toless than the time required for the stream buffer 2400 to empty,however, decoding can continue without data interruptions. This time atwhich the reading head 2006 can jump to another disk position without adata underflow state occurring in the stream buffer 2400 is referred toas the jump-enabled time.

Note that while physical movement of the reading head 2006 has beendescribed as a factor causing a data underflow state in the streambuffer 2400, the following factors also contribute. Note, further, thatthis data underflow state can be simply characterized as a condition inwhich data input to the track buffer (stream buffer 2400) does not keeppace with data output from the track buffer.

a) The buffer is too small relative to the decoding speed of thedecoder.

b) The sizes of the individual input units of the plural VOB typescarried in the reproduced bitstream St61 input to the stream buffer 2400from the bitstream producer 2000 are inappropriate for the buffer size.

c) The sequence of the individual input units of the plural VOB typescarried in the reproduced bitstream St61 is inappropriate for thedecoding speed, resulting in the next data unit to be decoded not beingreceived in sufficient time while decoding a particular data unit.

When the reproducing apparatus of the digital video disk system isconfigured with a disk read rate of 11 Mbps, a maximum AV datacompression rate of 10 Mbps, and a track buffer (stream buffer 2400)capacity of 4 Mbits, for example, a data underflow state will occur. Toprevent this data underflow state from occurring during the jump periodTj in a reproduction apparatus, thus configured with slight overflowcontrol maintained during normal continuous playback, a maximumjump-enabled time of 400 msec can be assured even in a worst-casescenario where 10 Mbps of AV data is reproduced during the jump period.

Note that a jump-enabled time of 400 msec is a realistic value that canbe achieved in actual reproduction apparatuses. In such an apparatus thedistance that can be jumped during a 400 msec period is approximately500 tracks. It follows that the jump-enabled time can also be defined indata quantity terms, specifically the volume of the sequential datastream that the reading head 2006 can move through within thejump-enabled time. The data volume equivalent to a 400 msec jump-enabledtime is approximately 250 Mbits. It will also be obvious that the actualdistance in sector and track units on the recording medium can also beeasily obtained from the data volume defined as the jumpable distancebased on the recording method and density of the recording medium.

A 250-Mbit jumpable distance is equivalent to a 50 sec. presentationtime assuming AV data reproduced at an average 5 Mbits/sec. With evenhigher quality AV data, the presentation time is less than 50 sec. Inmovies and other data streams edited to remove particular scenes due tocultural, educational, or other reasons, the excised scenes aretypically long, usually ranging from 2 to 5 minutes, and even as long as10 minutes. If the excised scene lasts 5 minutes, for example, with theabove reproduction apparatus, it is not possible to uninterruptedlyconnect the scenes before and after an excised scene if the beforescene, excised scene, and after scene are recorded to disk in a singlecontiguous series. More specifically, the data corresponding to acontinuous 5 minute scene cannot be jumped in a single jump operation.

There are also cases in which the AV data compression rate, i.e., theconsumption rate Vo of data from the track buffer, approaches 10 Mbpsand non-occurrence of a buffer underflow state cannot be assured, evenwhen the excised scene data is jumped using a jump period Tj exceeding400 msec. While such a data underflow state can conceivably be avoidedby recording two AV data scenarios, i.e., excised (edited) andun-excised (unedited) scenarios, to disk, this method does not makeeffective use of the available disk capacity. If it is also necessary torecord duplicate data for much presentation time, the AV data will below quality and it will be difficult to satisfy most user expectations.

The concept of sharing data between plural titles is described belowwith reference to FIG. 33 wherein TL1 and TL2 refer to the data contentof a first and second title, respectively. Specifically, the first titleTL1 consists of data DbA, DbB, and DbD reproduced contiguously duringtime T, and the second title TL2 similarly consists of data DbA, DbC,and DbD reproduced contiguously during time T. Note that data DbA, DbB,DbC, and DbD are video objects VOB with display times T1, T2, T2, andT3, respectively. When two titles TL1 and TL2 thus comprised arerecorded to disk, the data stream is structured with data DbA and DbD asshared data of both titles TL1 and TL2, and data DbB and DbC as thediscrete data of titles TL1 and TL2, respectively, selectivelyreproduced during selection period T2 as shown by title TLl_2. Note thatwhile there appears to be a time gap between the data blocks in FIG. 33,this is simply to facilitate the use of arrows in the figure for easierdescription of the data reproduction paths. There is no actual time gapduring playback.

The format whereby these data blocks DbA, DbB, DbC, and DbD are recordedto disk in title TL1_2 to enable contiguous reproduction of the data isshown in FIG. 34. In principle, data blocks DbA, DbB, DbC, and DbDcomposing a single contiguous title are recorded to contiguous segmentsof the data recording track TR (FIG. 9). Thus, data DbA, DbB, and DbD offirst title TL1 are first recorded contiguously, and are followed bydata DbC unique to the second title TL2. With this data format, thefirst title TL1 can be contiguously reproduced without breaks in thetitle content, i.e., seamlessly, by means of controlling the readinghead 2006 to access data DbA, DbB, and DbD synchronized to playbackperiods T1, T2, and T3, respectively.

To reproduce the second title TL2, however, the reading head 2006 mustjump past (data DbB and DbD after reproducing data DbA in period T1, andmust reach data DbC before the start of period T2 as shown by arrow Sq2a in FIG. 34. Then after reproducing data DbC, the reading head 2006must jump back to data units DibC and DbD as shown by arrow Sq2 b, andreach data DbD before the start of period T3. Because of the timerequired to) move the reading head 2006 between data blocks, it is notpossible to assure seamless reproduction between data DbA and DbC, andbetween DbC and DbD, unless the distance travelled between these datablocks requires less time than the time required for a data underflowstate to occur in the stream buffer 2400.

To thus enable the user to selectively excise scenes and choose fromamong plural scenes, a state wherein non-selected scene data is recordedinserted between common scene data and selective scene data necessarilyoccurs because the data units associated with individual scenes arecontiguously recorded to the recording tracks of the recording medium.If data is then read in the recorded sequence, non-selected scene datamust be accessed before accessing and decoding the selected scene data,and seamless connections with the selected scene is difficult. Theexcellent random access characteristics of the digital video disksystem, however, make seamless connections with the selected scenespossible.

In other words, by splitting scene-specific data into plural units of aspecified data size, and interleaving plural split data units fordifferent scenes in a predefined sequence that is recorded to diskwithin the jumping range whereby an data underflow state does not occur,it is possible to reproduce the selected scenes without datainterruptions by intermittently accessing and decoding the data specificto the selected scenes using these split data units. Seamless datareproduction is thereby assured.

The seamless connection method and data splitting and arraying conceptsof the present invention are described below using the track bufferinput transfer rate Vr and data consumption rate Vo described above.

Referring again to FIG. 32, the data consumption rate Vo is less thanthe transfer rate Vr (Vr>Vo). Using this difference, a known data volumeis read at the transfer rate Vr, buffered to the track buffer andstored, and is then consumed (output to the decoder) while the opticalpickup moves to the position of the next read data. To prevent a dataunderflow state even after multiple repetitions of this operation, splitdata units for a defined volume of data for each scene are distributedat an appropriate interval. This method of arraying data to assureseamless data reproduction is called “interleaving,” the split dataunits of a size sufficient for buffering to the track buffer are called“interleave units,” and the interleave units after interleaving arecalled “interleaved units.”

When one scene is selected from plural scenes, interleave units arerequired for tile plural video objects VOBs composing those pluralscenes. Two interleaved units ILVU contiguous on the time-base andbelonging to the selected scene are separated by one or more interleavedunits ILVU belonging to another scene, inserted therebetween. Thedistance between two time-base-contiguous interleaved units ILVUbelonging to the same scene is defined as the interleave distance.

For example, 260 msec is required to move 10,000 sectors using anoptical disk recording medium. If this 10,000-sector movement of theoptical pickup is the interleave unit distance, the size of theinterleaved units ILVU can be determined from the difference between thetrack buffer input and output transfer rates Vr and Vo, and the size ofthe track buffer. Let us assume, for example, that compressed data isbeing output at a constant rate using an input transfer rate Vr of 11Mbps and an output transfer rate Vo of 8 Mbps, and a track buffercapacity of 3 Mbits. If the distance between interleaved units ILVU is10,000 sectors, there must be enough interleaved units ILVU to input tothe track buffer to accumulate therein a 260-msec equivalent of playbackdata before the reading head moves.

In general, 2080 Kbits is equivalent to 260 msec of playback data. Tostore this much data to the track buffer before moving betweeninterleaved units ILVU, source data must be input to the track bufferfor 0.7 sec. at the difference between transfer rates Vr and Vo (=2080Kbit/(11−8) Mbits/sec). The time needed to read enough source data fromthe recording medium M to store sufficient data to the track buffer toprovide for data consumption by the decoder while the optical pickup ismoving to the target interleaved unit ILVU and can resume data readingis defined as the minimum accumulation read time.

The minimum interleaved unit size, i.e., the amount of data that must beread, is therefore 7.7 Mbits. Converted to presentation time, this makesit possible to interleave units with a presentation time of 0. 96 sec.or greater with presentation time intervals less than 20 sec. betweeninterleaved units. By reducing the system stream consumption bit rate,the minimum accumulation read time can be reduced, and the size of theinterleaved units can be reduced. It is also possible to increase thejumpable time without changing the interleaved unit size.

One method of connecting scenes is shown in FIG. 35 where the followingscenarios are possible: scene A connected to scene D; scene A connectedto scene B, which is substituted for a certain time segment of scene D;and scene A connected to scene C, which is similarly substituted for acertain time segment of scene D but for a different time segment thanscene B. In such cases, scene D is further blocked into scene segments(scenes) D-1, D-2, and D-3. The system stream corresponding to scenes B,D-1, C, and D-2 is the output system stream output at transfer rate Vo(=8 Mbps). Data is input to the track buffer at transfer rate Vr (=11Mbps) in the scene sequence B. D-1, C, D-2; the data size of each sceneis greater than the above value (=0,96 sec.), and can be arrayed withinthe distance that can be jumped between connected scenes as describedabove.

However, when scenes with the same starting points but different endpoints, e.g., scenes B, C, and D in this example, are interleaved, threedifferent system streams become interleaved during the periodcorresponding to scene D-1, two system streams become interleaved duringthe period corresponding to scene D-2, and processing tends to becomecomplex. It is therefore more common when interleaving plural videoobjects VOB to interleave objects having the same starting and endpoints, thus simplifying processing. This can be accomplished as shownin FIG. 36 by copying and appending scene D-2 to scene C of FIG. 35,thereby unifying the points at which plural scenes diverge and connect,i.e., the starting and end points, with plural interleaved video objectsVOB. When interleaving branching and connecting scenes in the digitalvideo disk system, therefore, the scenes are interleaved with thestarting and end points thereof aligned.

The interleaving concept is described in further detail below.

The audio-video (AV) system stream described above is one example ofinterleaving with time information. This interleaving method arraysaudio and video information having the same time-base so that data inputto the buffer at approximately the same time is in physical proximity,and data units having approximately the same presentation time arearrayed in alternating sequence. When one scene can be replaced withanother scene in titles such as movies, however, the time between theseplural scenes often differs. When the AV system stream interleavingmethod described above is applied in such cases, the between-scene timedifference can be absorbed by the buffer if it is within the jumpabletime. If the between-scene time difference is greater than the jumpabletime, however, the buffer cannot absorb the difference and seamlessplayback is not possible.

If the track buffer size is increased to increase the amount of datathat can be accumulated at one time, a longer jumpable time is obtained,and the interleave unit and sequence are more easily determined. Wheninteractive operation enabling the user to select from among pluralscenes (e.g., multi-angle scenes) with seamless playback, thepresentation time of the previous angle stream is increased after theangle (stream) is changed if the interleaved units ILVU are made longerand the amount of data stored at one time is increased. This alsoresults in more time being required for the displayed stream to change.

Interleaving is thus the process of optimizing the system streamarrangement in data block units to prevent a data underflow state fromoccurring in the track buffer of the authoring decoder DC when theencoded data supplied from the stream source is consumed for decoding bythe decoder.

A major cause of this data underflow state is the mechanical movement ofthe optical pickup, though there are lesser factors such as the decodingspeed of the communications (decoding) system. Mechanical movement ofthe optical pickup is a problem when the optical pickup scans the datarecording track TR of the optical disk M to read data. Interleaving isalso needed when recording the data to the data recording track TR ofthe optical disk M. The decoding speed of the communications system canalso become a problem when the source stream is supplied directly asoccurs with live broadcasts, cable television and other dedicated linetransmissions, broadcast satellites and other radio wave transmissions,and other means whereby title content is not reproduced from a recordingmedium on the user's side. In such cases the transmitted source streammust be interleaved.

Interleaving can thus be more specifically defined as the processwhereby the data carried in a source stream comprising source datagroups of plural contiguously input source data blocks is arranged in aparticular sequence whereby the desired (targeted) source data can beintermittently and sequentially accessed to contiguously reproduce theinformation in the targeted source data. The duration of theseintermittent breaks in the input of the target source data that is to bereproduced is therefore defined as the jump time of the interleavecontrol.

It should be noted, hoiwever, that an interleaving method for arrayingon a random access disk movies and other common titles containing sceneselections that may branch and recombine according to various scenariosin a manner whereby video objects VOB containing video data compressedwith variable length coding has not been described. When arraying thistype of data to disk, a certain amount of trial and error is requiredusing the compressed data. This obviously makes it necessary to definean interleaving method for arranging plural video objects in a sequenceenabling seamless playback.

When applied to a DVD system as described above, these video objects aredistributed to positions (navigation packs NV) within a specifictime-base range bounded by GOP units, the unit of video datacompression. The GOP data length, however, may vary as a result ofuser-defined image manipulation processes or intra-frame coding insertedfor higher image quality. This means that the location of the managementpacks (navigation packs NV), which are dependent upon the presentationtime, can vary. This means that the point at which the scene anglechanges or the optical pickup jumps to the next data block in theplayback sequence is indefinite. Furthermore, if plural scene angles areinterleaved together, the length of contiguously read data is indefiniteeven if the next jump point is known. Thus, the data end point positionis known only after the next angle data is read, and switching theplayback data is thus delayed.

The present invention therefore provides a method and apparatus enablingseamless data reproduction using an optical disk having a data structurewhereby data is shared between plural titles to efficiently utilize theavailable optical disk space, and a new function called “multi-anglescene reproduction” is achieved. The method and apparatus of the presentinvention are described below with reference to the accompanyingfigures.

The interleaving method enabling seamless data reproduction according tothe present invention is described below with reference to FIG. 24 andFIG. 37. Shown in FIG. 24 is a case from which three scenarios may bederived, i.e., branching from one video object VOB-A to one of pluralvideo objects VOB-B, VOB-C, and VOB-D, and then merging back again to asingle video object VOB-E. The actual arrangement of these blocksrecorded to a data recording track TR on disk is shown in FIG. 37.

Referring to FIG. 37, VOB-A and VOB-E are video objects with independentplayback start and end times, and are in principle arrayed to contiguousblock regions. As shown in FIG. 24, the playback start and end times ofVOB-B, VOB-C, and VOB-D are aligned during interleaving. The interleaveddata blocks are then recorded to disk to a contiguous interleaved blockregion. The contiguous block regions and interleaved block regions arethen written to disk in the track path Dr direction in the playbacksequence. Plural video objects VOB, i.e., interleaved video objectsVOBS, arrayed to the data recording track TR are shown in FIG. 37.

Referring to FIG. 37, data regions to which data is continuously arrayedare called “blocks,” of which there are two types: “contiguous blockregions” in which VOB with discrete starting and end points arecontiguously arrayed, and “interleaved block regions” in which pluralVOB with aligned starting and end points are interleaved. The respectiveblocks are arrayed as shown in FIG. 38 in the playback sequence, i.e.,block 1, block 2, block 3, . . . block 7.

As shown in FIG. 39, the VTS title VOBS (VTSTT_VOBS) consist of blocks1-7, inclusive. Block 1 contains VOB 1 alone. Blocks 2, 3, 5, and 7similarly discretely contain VOBS 2, 3, 6, and 10. Blocks 2, 3, 5, and 7are thus contiguous block regions.

Block 4, however, contains VOB 4 and VOB 5 interleaved together, whileblock 6 contains VOB 7, VOB 8, and VOB 9 interleaved together. Blocks 4and 6 are thus interleaved block regions.

The internal data structure of the contiguous block regions is shown inFIG. 39 with VOB-i and VOB-j arrayed as the contiguous blocks in theVOBS. As described with reference to FIG. 16, VOB-i and VOB-j inside thecontiguous block regions are further logically divided into cells as theplayback unit. Both VOB-i and VOB-j in this figure are shown comprisingthree cells CELL #1, CELL #2, and CELL #3.

Each cell comprises one or more video object unit VOBU with the videoobject unit VOBU defining the boundaries of the cell. Each cell alsocontains information identifying the position of the cell in the programchain PGC (the playback control information of the digital video disksystem). More specifically, this position information is the address ofthe first and last VOBU in the cell. As also shown in FIG. 39, these VOBand the cells defined therein are also recorded to a contiguous blockregion so that contiguous blocks are contiguously reproduced.Reproducing these contiguous blocks is therefore no problem.

The internal data structure of the interleaved block regions is shown inFIG. 40. In the interleaved block regions each video object VOB isdivided into interleaved units ILVU, and the interleaved units ILVUassociated with each VOB are alternately arrayed. Cell boundaries aredefined independently of the interleaved units ILVU. For example, VOB-kis divided into four interleaved units ILVUk1, ILVUk2, ILVUk3, andILVUk4, and are confined by a single cell CELL#k. VOB-k is likewisedivided into four interleaved units ILVUm1, ILVUm2, ILVUm3, and ILVUm4,and is confined by a sincle cell CELL#m. Note that instead of a singlecell CELL#k or CELL#m, each of VOB-k and VOB-m can be divided into morethan two cells. The interleaved units ILVU thus contains both audio andvideo data.

In the example shown in FIG. 40, the interleaved units ILVUk1, ILVUk2,ILVUk3, and ILVUk4, and ILVUm1, ILVUm2, ILVUm3, and ILVUm4, from twodifferent video objects VOB-k and VOB-m are alternately arrayed within asingle interleaved block. By interleaving the interleaved units ILVU oftwo video objects VOB in this sequence, it is possible to achieveseamless reproduction branching from one scene to one of plural scenes,and from one of plural scenes to one scene.

This interleaving process further enables seamless reproduction ofscenes from various scenario threads in most cases. Seamlessreproduction is even possible when there are three possible scenariothreads as shown in FIG. 35, i.e., from scene A to scene B, and then toscene D-3 starting at some midpoint in scene D; from scene A to thebeginning of scene D; and from scene A to scene C, and then to scene D-2starting at a midpoint in scene D different from D-3. As shown in FIG.36, it is also possible by connecting before and after scenes (sceneD-2) to align the starting and end points according to the datastructure of the present invention. Note that this process of copyingscenes to align the starting and end points makes it possible toseamlessly reproduce even complicated threading of different scenes.

An example of an interleaving algorithm compatible with variable lengthcoded data, i.e., video data, is described next.

When plural VOB are interleaved, each VOB is basically divided into thesame particular number of interleave units. It is also possible toobtain the data volume (size) of each of this particular number ofinterleave units based on the bit rate of the VOB to be interleaved, thejump time and distance that can be jumped within this jump time, thetrack buffer capacity and the input rate Vr to the track buffer, and theposition of the video object unit VOBU. Each interleaved unit consistsof video object units VOBU, each of which comprises one or more MPEG GOPwith a data quantity equivalent to a 0.4-1.0 second presentation time.

When data is interleaved, the interleaved units ILVU forming separatevideo objects VOB are alternately arrayed. If any of the pluralinterleave units interleaved to the shortest of plural VOB is shorterthan the minimum interleave unit length, or if the total length ofplural interleave units in any but the shortest of plural VOB, isgreater than the shortest interleave distance, an underflow state willoccur when this shortest interleave VOB is reproduced, and non-seamlessreproduction will result instead of seamless reproduction.

Before encoding occurs in the present embodiment it is thereforedetermined whether interleaving is possible. Whether interleaving ispossible can be determined from the lengths of the pre-encoded streams.Because the effect of interleaving can thus be determined in advance,the need for data reprocessing, i.e., the need to adjust theinterleaving conditions and record after interleaving and encoding areonce completed, can be prevented.

The interleaving method for recording to an optical disk according tothe present invention is described specifically below, starting with thebit rate of the recorded VOB and the performance and other conditions ofthe reproduced disk.

When interleaving is applied, the relationship between the track bufferinput transfer rate Vr and output transfer rate Vo is defined as Vr>Voas previously described. The maximum bit rate of each VOB to beinterleaved is therefore set to less than the track buffer inputtransfer rate Vr. The maximum bit rate B of each VOB is therefore set toa value less than Vr. If in the evaluation determining whetherinterleaving enabling seamless reproduction is possible it is assumedthat all plural VOB to be interleaved are encoded with constant bit rate(CBR) coding at the maximum bit rate, the interleave unit data volume ismaximized, the time that can be reproduced from the data volume that canbe placed at the jumpable distance is shortened, and the interleaveconditions are stringent.

Note that it is assumed below that each VOB is encoded with constant bitrate (CBR) coding at the maximum bit rate.

It is assumed in the following description of the reproduction apparatusthat the distance the optical pickup can jump within disk jump time JTexpressed as a data quantity is jumpable distance JM, and the input databit rate to the track buffer of the reproduction apparatus is BIT.

In terms of an actual reproduction apparatus, the disk jump time JT is400 msec, the jumpable distance JM is 250 Mbit in this jump time JT. Themaximum bit rate B of the VOB in the MPEG system is defined as 8.8 Mbpsconsidering that an average 6 Mbps is required to obtain image qualitysuperior to that of a conventional VCR recording.

Based on the jumpable distance JM, jump time JT, -and data read timesfrom disk, the target values for the smallest interleaved unit sizeILVUM and the smallest interleave unit presentation time ILVUMT arecalculated first. The smallest interleave unit presentation time ILVUMTcan be obtained from equation 3, and the smallest interleaved unit sizeILVUM can be obtained from equation 4 below.

ILVUMT≧JT+ILVUM/BIT  [3]

ILVUMT×B=ILVUM  [4]

From equation 3 the smallest interleave unit presentation time ILVUMT isdetermined to be 2 sec., and the smallest GOP block data GM is 17.6Mbit. Thus, if the smallest interleave unit, which is the smallest unitof the data layout, is a 2-sec. equivalent data quantity and each GOPcomprises 15 frames (NTSC format), then the smallest interleave unit isequivalent to the data stored in four GOP.

As also stated above, one interleaving condition is that the interleavedistance be less than or equal to the jumpable distance. This means thatexcept for the VOB with the shortest presentation time, the totalpresentation time of plural VOB to which interleaving is applied must beshorter than the time that can be reproduced within the interleavedistance. If as in the above example the jumpable distance JM is 250Mbit and the maximum VOB bit rate is 8.8 Mbps, the time JMT that can bereproduced with the data quantity read within the jumpable distance JMis 28.4 sec. It is then possible to calculate an interleavableconditions equation using these values. If each VOB in the interleavedblock region is divided into the same number of interleaved block andthis number of interleaved divisions is v, equation 5 can be obtainedfrom the conditions of the smallest interleave unit length.

(presentation time of shortest VOB)/ILVUMT≦v[5]

Equation 6 can then also be obtained from the jumpable presentation timeconditions.

v≦(presentation time of all VOB except shortest VOB)/JMT  [6]

Plural VOB can in principle be interleaved if the above conditions arefulfilled. In practical terms, VOBU compensation to the value calculatedaccording to the above equations is necessary because the interleaveunits are limited to the VOBU boundaries. To compensate equations 2, 3,and 4, it is necessary to add the maximum VOBU time (1. 0 sec.) to thesmallest interleave unit presentation time ILVUMT, and reduce thepresentation time in the interleave distance JMT by the maximum VOBUtime.

If it is determined that an interleaved sequence enabling seamlessplayback is not possible as a result of calculating the conditions forinterleaving the VOB scenes before encoding, it is necessary to increasethe number of interleave unit divisions. This means increasing thelength of the scene forming the shortest VOB by moving the scenetherebefore or after. It is also necessary to add the same scene addedto the shortest scene to the other scenes. In general, the interleavedistance is significantly greater than the shortest interleave unit, andthe rate of increase in the value on the left side of equation 4 isgreater than the increase in the value on the right side of equation 6.As a result, increasing the size of the shifted (moved) scene can resultin satisfying the above conditions.

The track buffer input transfer rate Vr and output transfer rate Vo mustbe in the relationship Vr>Vo as described above for the data in theinterleaved blocks. The optical pickup may also jump immediately afterentering an interleaved block region from a contiguous block region, inwhich case it is also necessary to store the data from immediatelybefore the interleaved block region. This makes it necessary to suppressthe bit rate of part of the data in the VOB immediately before theinterleaved block region.

It is also possible that the optical pickup may jump immediately afterentering an interleaved block from a contiguous block, in which case itis necessary to suppress the maximum bit rate of the contiguous blockimmediately before the interleaved block, and store the data fromimmediately before the interleaved block to the track buffer. The targetfor suppressing the maximum bit rate, i.e., the amount the maximum bitrate is suppressed, is the presentation time of the shortest interleaveunit, which can be calculated from the maximum bit rate of theinterleaved block reproduced after the contiguous block.

Note that while the above operation has assumed that all VOB are dividedinto the same number of interleave units, it is also possible to groupthe VOB into a group of VOB containing u divisions (interleave units)and a group of VOB containing u+1 divisions when there is a significantdifference in VOB length.

This can be accomplished by defining the minimum number of divisions ineach VOB obtained from equation 5 as u and using this value u for allVOB from which a greater number of interleave units cannot be obtained,and using the number of interleave units obtained from equation 4 up to(u +1) for larger VOB. This is illustrated in FIG. 41.

The data structure of the interleaved unit ILVU in another embodiment ofthe invention is shown in FIG. 42. In. this structure the navigationpack NV described with reference to FIG. 20 is placed at the beginningof each video object unit VOBU, and the data from one navigation pack NVto immediately before the next navigation pack NV is defined as onevideo object unit VOBU. The video object unit VOBU boundaries determinethe boundaries of the interleaved unit ILVU, each of which is longerthan the length of the shortest interleaved unit, which is obtained fromthe decoder performance, bit rate, and other considerations usingequations 5 and 6.

Each of the component video object units VOBU contains a navigation packNV (management information pack), each navigation pack NV containing anILVU end pack address ILVU_EA indicating the address of the last pack inthe ILVU to which the VOBU belongs, and the next—ILVU start addressNT_ILVU_SA. The position to which the start address NT_ILVU_SA points isthe address of the first pack (NV) in the next interleaved unit ILVU tobe reproduced, while the ILVU end pack address ILVU_EA points to the endposition of the interleaved unit ILVU containing the end pack addressILVU_EA. Note that as previously described these addresses are expressedas the number of sectors from the navigation pack NV containing theaddress information.

When a video object unit VOBU is in an interleaved block region, thenext-ILVU start address NT_ILVU_SA points to the start address of thenext ILVU, similarly expressed as the number of sectors from thenavigation pack NV containing the address information.

It is therefore possible after reading the first navigation pack NV datain the interleaved unit ILVU to obtain the location of the nextinterleaved unit ILVU to be reproduced, and to what disk position thecurrent interleaved unit ILVU is written. This makes it possible to onlyread the interleaved units ILVU, and to smoothly jump to the nextinterleaved unit ILVU.

Multi-scene Control

The multi-scene period is described together with the concept ofmulti-scene control according to the present invention using by way ofexample a title comprising scenes recorded from different angles.

Each scene in multi-scene control is recorded from the same angle, butmay be recorded at different times or may even be computer graphicsdata. The multi-angle scene periods may therefore also be calledmulti-scene periods.

Parental Control

The concept of recording plural titles comprising alternative scenes forsuch functions as parental lock control and recording director's cuts isdescribed below using FIG. 43.

An example of a multi-rated title stream providing for parental lockcontrol is shown in FIG. 43. When so-called “adult scenes” containingsex, violence, or other scenes deemed unsuitable for children arecontained in a title implementing parental lock control, the titlestream is recorded with a combination of common system streams SSa, SSb,and Sse, an adult-oriented system stream SSc containing the adultscenes, and a child-oriented system stream SSd containing only thescenes suitable for children. Title streams such as this are recorded asa multi-scene system stream containing the adult-oriented system streamSsc and the child-oriented system stream Ssd arrayed to the multi-sceneperiod between common system streams Ssb and Sse.

The relationship between each of the component titles and the systemstream recorded to the program chain PGC of a title stream thuscomprised is described below.

The adult-oriented title program chain PGC1 comprises in sequence thecommon system streams Ssa and Ssb, the adult-oriented system stream Ssc,and the common system stream Sse. The child-oriented title program chainPGC2 comprises in sequence the common system streams Ssa and Ssb, thechild-oriented system stream Ssd, and the common system stream Sse.

By thus arraying the adult-oriented system stream Ssc and child-orientedsystem stream Ssd to a multi-scene period, the decoding methodpreviously described can reproduce the title containing adult-orientedcontent by reproducing the common system streams Ssa and Ssb, thenselecting and reproducing the adult-oriented system stream Ssc, and thenreproducing the common system stream Sse as instructed by theadult-oriented title program chain PGC1. By alternatively following thechild-oriented title program chain PGC2 and selecting the child-orientedsystem stream Ssd in the multi-scene period, a child-oriented title fromwhich the adult-oriented scenes have been expurgated can be reproduced.

This method of providing in the title stream a multi-scene periodcontaining plural alternative scenes, selecting which of the scenes inthe multi-scene period are to be reproduced before playback begins, andgenerating plural titles containing essentially the same title contentbut different scenes in part, is called parental lock control.

Note that parental lock control is so named because of the perceivedneed to protect children from undesirable content. From the perspectiveof system stream processing, however, parental lock control is atechnology for statically generating different title streams by means ofthe user pre-selecting specific scenes from a multi-scene period. Note,further, that this contrasts with multi-angle scene control, which is atechnology for dynamically changing the content of a single title bymeans of the user selecting scenes from the multi-scene period freelyand in real-time during title playback.

This parental lock control technology can also be used to enable titlestream editing such as when making the director's cut. The director'scut refers to the process of editing certain scenes from a movie to, forexample, shorten the total presentation time. This may be necessary, forexample, to edit a feature-length movie for viewing on an airplane wherethe presentation time is too long for viewing within the flight time orcertain content may not be acceptable. The movie director thusdetermines which scenes may be cut to shorten the movie. The title canthen be recorded with both a full-length, unedited system stream and anedited system stream in which the edited scenes are recorded tomulti-scene periods. At the transition from one system stream to anothersystem stream in such applications, parental lock control must be ableto maintain smooth playback image output. More specifically, seamlessdata reproduction whereby a data underflow state does not occur in theaudio, video, or other buffers, and seamless information reproductionwhereby no unnatural interruptions are audibly or visibly perceived inthe audio and video playback, are necessary.

Multi-angle Control

The concept of multi-angle scene control in the present invention isdescribed next with reference to FIG. 44. In general, multimedia titlesare obtained by recording both the audio and video information(collectively “recording” below) of the subject over time T. The angledscene blocks #SC1, #SM1, #SM2, #SM3, and #SC3 represent the multimediascenes obtained at recording unit times T1, T2, and T3 by recording thesubject at respective camera angles. Scenes #SM1, #SM2, and #SM3 arerecorded at mutually different (first, second, and third) camera anglesduring recording unit time T2, and are referenced below as the first,second, and third angled scenes.

Note that the multi-scene periods referenced herein are basicallyassumed to comprise scenes recorded from different angles. The scenesmay, however, be Id recorded from the same angle but at different times,or they may be computer graphics data. The multi-angle scene periods arethus the multi-scene periods from which plural scenes can be selectedfor presentation in the same time period, whether or not the scenes areactually recorded at different camera angles.

Scenes #SC1 and #SC3 are scenes recorded at the same common camera angleduring recording unit times T1 and T3, i.e., before and after themulti-angle scenes. These scenes are therefore called “common anglescenes.” Note that one of the multiple camera angles used in themulti-angle scenes is usually the same as the common camera angle.

To understand the relationship between these various angled scenes,multi-angle scene control is described below using a live broadcast of abaseball game for example only.

The common angle scenes #SC1 and #SC3 are recorded at the common cameraangle, which is here defined as the view from center field on the axisthrough the pitcher, batter, and catcher.

The first angled scene #SM1 is recorded at the first multi-camera angle,i.e., the camera angle from the backstop on the axis through thecatcher, pitcher, and batter. The second angled scene #SM2 is recordedat the second multi-camera angle, i.e., the view from center field onthe axis through the pitcher, batter, and catcher. Note that the secondangled scene #SM2 is thus the same as the common camera angle in thisexample. It therefore follows that the second angled scene #SM2 is thesame as the common angle scene #SC2 recorded during recording unit timeT2. The third angled scene #SM3 is recorded at the third multi-cameraangle, i.e., the camera angle from the backstop focusing on the infield.

The presentation times of the multiple angle scenes #SM1, #SM2, and #SM3overlap in recording unit time T2; this period is called the“multi-angle scene period.” By freely selecting one of the multipleangle scenes #SM1, #SM2, and #SM3 in this multi-angle scene period, theviewer is able to change his or her virtual viewing position to enjoy adifferent view of the game as though the actual camera angle is changed.Note that while there appears to be a time gap between common anglescenes #SC1 and #SC3 and the multiple angle scenes #SM1, #SM2, and #SM3in FIG. 44, this is simply to facilitate the use of arrows in the figurefor easier description of the data reproduction paths reproduced byselecting different angled scenes. There is no actual time gap duringplayback.

Multi-angle scene control of the system stream based on the presentinvention is described next with reference to FIG. 23 from theperspective of connecting data blocks. The multimedia data correspondingto common angle scene #SC is referenced as common angle data BA, and thecommon angle data BA in recording unit times T1 and T3 are referenced asBA1 and BA3, respectively. The multimedia data corresponding to themultiple angle scenes #SM1, ISM2, and #SM3 are referenced as first,second, and third angle scene data MA1, MA2, and MA3. As previouslydescribed with reference to FIG. 44, scenes from the desired angled canbe viewed by selecting one of the multiple angle data units MA1, MA2,and MA3. There is also no time gap between the common angle data BA1 andBA3 and the multiple angle data units MA1, MA2, and MA3.

In the case of an MPEG system stream, however, intermittent breaks inthe playback information can result between the reproduced common andmultiple angle data units depending upon the content of the data at theconnection between the selected multiple angle data unit MA1, MA2, andMA3 and the common angle data BA (either the first common angle data BA1before the angle selected in the multi-angle scene period or the commonangle data BA3 following the angle selected in the multi-angle sceneperiod). The result in this case is that the title stream is notnaturally reproduced as a single contiguous title, i.e., seamless datareproduction is achieved but non-seamless information reproductionresults.

The multi-angle selection process whereby one of plural scenes isselectively reproduced from the multi-angle scene period with seamlessinformation presentation to the scenes before and after is describedbelow with application in a digital video disk system using FIG. 23.

Changing the scene angle, i.e., selecting one of the multiple angle dataunits MA1, MA2, and MA3, must be completed before reproduction of thepreceding common angle data BA1 is completed. It is extremely difficult,for example, to change to a different angle data unit MA2 duringreproduction of common angle data BA1. This is because the multimediadata has a variable length coded MPEG data structure, which makes itdifficult to find the data break points (boundaries) in the selecteddata blocks. The video may also be disrupted when the angle is changedbecause inter-frame correlations are used in the coding process. Thegroup_of_pictures GOP processing unit of the MPEG standard contains atleast one refresh frame, and closed processing not referencing framesbelonging to another GOP is possible within this GOP processing unit.

In other words, if the desired angle data, e. g., MA3, is selectedbefore reproduction reaches the multi-angle scene period, and at thelatest by the time reproduction of the preceding common angle data BA1is completed the angle data selected from within the multi-angle sceneperiod can be seamlessly reproduced. However, it is extremely difficultwhile reproducing one angle to select and seamlessly reproduce anotherangle within the same multi-angle scene period. It is thereforedifficult when in a multi-angle scene period to dynamically select adifferent angle unit presenting, for example, a view from a differentcamera angle.

The method of switching between scene angles within a multi-angle sceneperiod is described in further detail below with reference to FIG. 76,FIG. 77, and FIG. 45 based on the digital video disk data structuredescribed above.

FIG. 76 shows the presentation times of the smallest angle switchingunits in each of the multiple angle data units MA1, MA2, and MA3 shownin FIG. 23. Within the context of the digital video disk system, themultiple angle data units MA1, MA2, and MA3 are the title editing units,i.e., the video objects VOB. Each multiple angle data unit (VOB)comprises plural (three in this example) interleave units ILVU as thesmallest possible angle switching unit. Note that each interleaved unitILVU thus contains a particular number of GOP. The first angle data MA1thus contains angle switching units A51, A52, and A53.

The angle switching units A51, A52, and A53 of the first angle data MA1have presentation times of 1, 2, and 3 seconds, respectively, resultingin the first angle data MA1 having a total presentation time of 6 sec.The second angle data MA2 similarly comprises angle switching units B51,B52, and B53 with presentation times of 2, 3, and 1 second,respectively, and the third angle data MA3 comprises angle switchingunits C51, C52, and C53 with presentation times of 3, 1, and 2 seconds,respectively. It should be noted that while the angle data MA1, MA2, andMA3 each has a 6 sec. presentation time, the presentation time canobviously be set to various other particular values.

The following example describes switching to and beginning thepresentation of another (next) angle view while reproducing anyparticular interleave unit. For example, if the angle is changed fromfirst angle data MA1 to second angle data MA2 while reproducinginterleave unit A51, reproduction of interleave unit A51 stops andreproduction of the second interleave unit B52 in the selected secondangle data MA2 starts. This change intermits both the audio and videopresentation, resulting in non-seamless information presentation.

Likewise, if the user chooses to switch to the scene corresponding tothe third angle data MA3 during reproduction of the second interleaveunit B52 in the second angle data MA2, reproduction of interleave unitB52 stops and reproduction of interleave unit C53 starts. This operationagain intermits both the audio and video presentation, resulting innon-seamless information presentation.

Note that in the above cases switching between multiple angle dataduring data reproduction stops reproduction of the angle beingpresented, and seamless information presentation, i.e., presentationwithout intermitting the audio and video, does not occur.

The method of switching the angle after completing interleave unitpresentation is described below.

If the user selects second angle data MA2 during reproduction ofinterleave unit AS1 in first angle data MA1, for example, the secondinterleave unit B52 in the second angle data MA2 is selected from thepoint reproduction of interleave unit A51 with a presentation time of 1sec. is completed. Because the start of interleave unit B52 is 2 sec.from the beginning of the multi-angle scene period, there is a gapbetween the end of interleave unit A51 reproduction at 1 sec. into themulti-angle scene period and the beginning of interleave unit B52 at 2sec. into the multi-angle scene period, and there is therefore notime-base contiguity in reproduction. More specifically, because thereis no continuity in the audio, the audio cannot be seamlesslyreproduced.

A similar scenario results if the user then switches to the angle scenecorresponding to the third angle data MA3 during reproduction of thesecond interleave unit B52 in the selected second angle data MA2, i.e.,interleave unit C53 is switched to after reproduction of interleave unitB52 is completed. In this case the completion of interleave unit B52reproduction is at 5 sec. from the beginning of the multi-angle sceneperiod, the beginning of interleave unit C53 is at 4 sec. from thebeginning of the multi-angle scene period, and there is again notime-base contiguity. The connection between the audio and videocomponents of the interleave units B52 and C53 is also not good.

It is therefore necessary for the interleave units of each angle to havethe same reproduction time and contain the same number of video framesin order to achieve seamless information switching between multipleangles.

The internal structure of the interleave units is shown in furtherdetail in FIG. 77. As shown in FIG. 77, each of the interleave unitsILVUb1, ILVUb2, ILVUc1, and ILVUc2 contains interleaved audio and videopackets, indicated as A and V, respectively.

In general, the data size and presentation time of each audio packet Ais the same. In this example, interleave units ILVUb1, ILVUb2, ILVUc1,and ILVUc2 respectively contain 3, 2, 2, and 3 audio packets. Therefore,angle data MAB and MAC each contain 5 audio packets and 13 video packetsin multi-angle scene period T2.

Angle switching control within a multi-angle scene period comprising amulti-angle system stream (VOB) with this packet structure is describedbelow.

If the angle is switched from interleaved unit ILVUb1 to interleavedunit ILVUc2, for example, the total number of audio packets in these twointerleave units ILVUb1 and ILVUc2 is 6, which is one more than thespecified total number of 5 audio packets in this multi-angle sceneperiod T2. This would therefore result in an overlap of one audio packetin the reproduced audio if these two ILVU were connected and reproduced.Likewise, if the angle is changed between the two interleaved unitsILVUc1 and ILVUb2 containing only two audio packets each, the total of 4audio packets is one less than the specified total number of 5 audiopackets in this multi-angle scene period T2. Connecting and reproducingthese two interleaved units would therefore result in an audio packetshortage, and a break in the audio equal to the duration of one audiopacket. It is therefore clear that when the number of audio packets inthe connected interleaved units is not equal to the specified number ofaudio packets in that multi-angle scene period, the audio will not besatisfactorily connected, and non-seamless information presentationcontaining noise and/or intermittent audio will result.

FIG. 45 shows multi-angle scene control when the multi-angle data MABand MAC shown in FIG. 77 contain different audio data. Common angle dataBA1 and BA3 contain the common audio data of the common scenes beforeand after the multi-angle scene period. The first angle data MABcomprises first angle interleave unit audio data ILVUb1 and ILVUb2, thesmallest angle switching unit within the multi-angle scene period. Thesecond angle data MAC likewise comprises second angle interleave unitaudio data ILVUc1 and ILVUc2.

FIG. 14 shows the audio waves resulting from the audio data recorded tothe multi-angle data MAB and MAC within multi-angle scene period T2. Thecontiguous audio output of angle data MAB is formed from the twointerleaved unit audio data ILVUb1 and ILVUb2. The contiguous audiooutput of angle data MAC is likewise formed from the two interleavedunit audio data ILVUc1 and ILVUc2.

What happens when reproduction of angle data MAC is switched to duringreproduction of the first interleave unit audio data ILVUb1 in angledata MAB is described below. In this case reproduction of interleavedunit ILVUc2 occurs after reproduction of interleaved unit ILVUb1 iscompleted. As a result, the audio wave resulting from these twointerleaves units is a mixed wave as shown by audio wave MAB-C in FIG.12. Note that the resulting audio output wave is non-contiguous at theangle switching point, and the audio connection is therefore notcompletely satisfactory.

If the audio data is encoded using Dolby AC-3 coding, the problems areeven greater because AC-3 coding use time-base correlations.Specifically, because the audio is coded using time-base signalcorrelations, reproduction becomes impossible at the angle switchingpoint when the user attempts to stop the audio data from one angle andswitch to the audio data of another angle during reproduction in amulti-angle scene period.

Thus, when each angle in a multi-angle scene period contains discreteaudio data, the audio output may be intermitted between the connecteddata units when the angle is changed. Depending on the content of thedata in such cases, noise and/or audio interruptions may occur duringreproduction, resulting even in irritation or discomfort to the user.Such discomfort is a product of the non-contiguity in the reproducedinformation content, and can therefore be avoided by assuringinformation contiguity or preventing information intermittence. Seamlessinformation presentation can thus be achieved.

Multi-angle scene control according to the present invention isdescribed next with reference to FIG. 46. Three angle data MA1, MA2, andMA3 are written to multi-angle scene period T2 in this example.

The first angle data MA1 thus contains angle switching units A11, A12,and A13 as the smallest possible angle switching units. These angleswitching units AS1, A52, and A53 have presentation times of 2, 1, and 3seconds, respectively.

The second angle data MA2 similarly comprises angle switching units B11,B12, and B13, and the third angle data MA3 comprises angle switchingunits C11, C12, and C13. Each of these angle switching units alsorespectively have presentation times of 2, 1, and 3 seconds.

Because the synchronized interleave units thus have the samepresentation times, contiguous audio and video reproduction can beachieved without interruptions or overlaps at the angle switchingposition even when the user switches from one angle to another angle,and seamless information presentation can therefore be achieved aspreviously described.

To achieve the data structure shown in FIG. 46, i.e., to set the actualpresentation times of the smallest angle switching units of the audioand video material in the multi-angle scene period to the same times,the number of reproduction frames in each interleave unit must be thesame. MPEG data compression normally operates on the GOP unit level, andtwo parameters defining the GOP structure are the M and N values. M isthe I- or P-picture cycle, and N is the number of frames contained inthat GOP. Furthermore, changing the M or N parameter setting frequentlyduring the encoding process simply complicates MPEG video encodingcontrol, and is not, therefore, normally done.

A method of achieving the data structure shown in FIG. 46, i.e., amethod of setting the actual presentation times of the smallest angleswitching units of the audio and video material in the multi-angle sceneperiod to the same times, is described below with reference to FIG. 78.

As the example shown in FIG. 78 writes two angle data units MAB and MACto the multi-angle scene period, and each angle data unit comprises twointerleaved units ILVUb1 and ILVUb2, and ILVUc1 and ILVUc2,respectively. This is for simplicity of discussion only. Eachinterleaved unit is a GOP structure. The GOP structures in themulti-angle scene period set the M and N parameters of the synchronizedinterleaved units ILVUb1 and ILVUc1 to the same values, and similarlyset the M and N parameters of the synchronized interleaved units ILVUb2and ILVUc2 to the same values. By thus using the same GOP structureparameters in both angle data MAB and MAC, the presentation times of theAV data in different angles can be set to the same on the smallest angleswitching unit level. Thus, when the angle is changed from first angledata MAB ILVUb2 to angle data MAC ILVUc2, contiguous video presentationwithout video intermittence or overlap at the angle switching positioncan be achieved because the angle switching timing between these twoILVU is the same.

A method for actually setting the audio data presentation times on thesmallest angle switching unit level to the same value in differentangles is described next with reference to FIG. 79. As in FIG. 77, theinterleave units ILVUb1, ILVUb2, ILVUc1, and ILVUc2 contain interleavedaudio and video packets, indicated as A and V, respectively.

The audio packet A data size and presentation times are normallyconstant. As also shown in the figure, ILVUb1 and ILVUc1 in themulti-angle scene period have the same number of audio packets (2), andILVUb2 and ILVUc2 have the same number of audio packets (3). By thuswriting the same number of audio packets to the synchronized interleavedunits ILVU of different angle data MAB and MAC, the audio datapresentation times can be set the same on the smallest angle switchingunit level in different angles. Thus, when the view is changed betweenangle data MAB and MAC, contiguous audio presentation without audiointermittence or overlap at the angle switching position can be achievedbecause the angle switching timing does not change.

However, if each of the smallest angle switching units in themulti-angle scene period contain audio data describing discrete audiowaves, it may not be possible (as described above with reference to FIG.12) to achieve contiguous audio data reproduction at the angle switchingpoint by simply coding each smallest angle switching unit (ILVU) withthe same audio data presentation time. It is possible to avoidintermitting the audio presentation, however, by writing the same(common) audio data to each angle within a multi-angle scene period onthe smallest angle switching unit (ILVU) level. As previously described,seamless information presentation can be achieved by arraying the datato assure contiguous information content before and after the connectionpoints in the reproduced data, or by formatting the data in closed dataunits that are completely reproduced at the switching points.

A further multi-angle scene period data structure in which common audiodata is written to each different angle is shown in FIG. 80. Unlike thestructure shown in FIG. 45, this data structure is achieved by writingaudio data that is complete within each switching unit (interleaved unitILVU) to the angle data MAB and MAC.

Because the audio data is thus complete within each interleaved unitILVU, audio data producing a discomforting audio wave as a result ofconnecting different audio waves at the angle switching point will notresult even when the angle is changed by switching from first angleinterleaved unit ILVUb1 to second angle interleaved unit ILVUc2 withinan encoded audio data multi-angle scene period thus structured.

Note that if the audio data is formed with the same audio wave on theinterleaved unit ILVU level, seamless information presentation canobviously be achieved just as when the audio wave data is completewithin each interleaved unit ILVU.

When the audio data is coded using Dolby AC-3 audio coding, thetime-base correlations can be retained even when the angle is changed,and contiguous audio reproduction can be achieved at the angle switchingpoint without noise or intermittence, because common audio data iswritten to the smallest angle switching units (ILVU) of the angle dataor is complete within each interleaved unit ILVU.

It should be noted that the present invention shall not be limited toonly two or three types of angle data MA within the multi-angle sceneperiod. The multi-angle scene period T2 shall also not be limited to VOBunits, and may extend for the duration of the title stream.

It is therefore possible to achieve seamless information presentation aspreviously defined.

The operation of multi-angle control based on the digital video diskdata structure is thus as described above.

A method of recording to the recording medium multi-angle control dataspecifically enabling selection of a different angle data unit whilereproducing one angle data unit in the same multi-angle scene period is,however, described below.

The common angle data BA1 shown in FIG. 23 is arrayed to a contiguousblock region, the interleave unit data of the multi-angle data MA1, MA2,and MA3 in the multi-angle scene period is arrayed to an interleavedblock region, and the common angle data BA3 following thereafter isarrayed to the next contiguous block region. Referenced to the datastructure shown in FIG. 16, the common angle data BA1 constitutes onecell, the multi-angle data MA1, MA2, and MA3 each constitute one cell,the cells corresponding to the multi-angle data MA1, MA2, and MA3constitute one cell block (the cell block mode CBM of the MA1 cell=“cellblock start”, the CBM of the MA2 cell=“between first and last cells”;and the CBM of the MA3 cell “cell block end”), and these cell blocks areangle blocks (cell block type CBT=angle). The common angle data BA3 isthe cell that connects to that angle block. The cell-cell connectionsare also set for seamless playback (seamless playback flag SPF=“seamlessplayback”).

The structure of the stream containing a multi-angle scene period andthe basics of the on-disk layout in the preferred embodiment of theinvention are shown in FIG. 47. The multi-angle scene period is a periodin which the stream can be freely changed by the user. In a stream withthe structure shown in FIG. 47, it is possible to switch to VOB-C orVOB-D during reproduction of VOB-B. It is therefore likewise possible toswitch to VOB-B or VOB-D during reproduction of VOB-C, and to switch toVOB-C or VOB-B during reproduction of VOB-D.

As previously described, the unit for changing the angle, i. e., theangle selection unit, is the smallest interleave unit obtained from theconditions defined by equations 3 and 4, and is defined as the angleinterleave unit A-ILVU. A-ILVU management information is also added tothe angle interleave unit A-ILVU. The navigation pack NV previouslydescribed corresponds to this A-ILVU management information.

An example in which the last pack address in the current A-ILVU and theaddress of the next A-ILVU are recorded for plural angles is shown asanother embodiment of the invention in FIG. 48. While this figure isvery similar to FIG. 42, the angle interleave unit A-ILVU comprises twovideo object units VOBU in this example, and the navigation pack NV ofeach VOBU contains the ILVU end pack address ILVU_EA indicating theaddress of the last pack in the ILVU to which the VOBU belongs, and thenext-ILVU start address for each angle data block #1-#9(SML_AGL_Cl_DSTA-SML AGL_C9_DSTA). These addresses are expressed as thenumber of sectors from the navigation pack NV containing the addressinformation. In fields in which there is no angle data, informationindicating that there is no angle data, e.g., 0, is recorded. By thusrecording the last pack address and the next-ILVU start address for eachangle data block #1-#9, it is possible to know the address of each nextselectable angle and to switch to a different angle scene withoutreading unnecessary angle information.

For interleaving data in the multi-angle scene period, all angles areinterleaved to the same time reference (interleave boundary) using theangle interleave unit A-ILVU for the shortest read time. This is toenable the angle to be changed as quickly as possible within theperformance limits of the DVD player. Interleave unit data istemporarily stored to the track buffer, and the data for the angleselected next is then input to the track buffer. However, the next anglecannot be reproduced until the data for the previous angle (the anglebeing reproduced when the angle was changed) in the track buffer hasbeen consumed. It is therefore necessary to minimize the size of theangle interleave unit A-ILVU in order to maximize the speed at which thenext angle scene can be selected and presented. A common interleave unitsize and boundary position must therefore be used between the VOBconstituting each angle.

This means that the reproduction time of the encoded video streamforming the VOB must be the same for each VOB, and the time at whicheach interleave unit can be reproduced must be the same, i.e., theinterleave unit boundaries must be common, for each interleave unit atthe same reproduction time in each angle. More specifically, the VOBsconstituting each angle must be divided into the same number ofinterleave units, and the reproduction time of said interleave unitsmust be the same in each angle, i.e., the VOBs constituting each anglemust be divided into the same number N of interleave units, and the k-thinterleave unit (where 1≦k≦N) in each angle must have the samereproduction time.

Moreover, to seamlessly reproduce the interleave units between eachangle, the encoded stream must be complete within each interleave units.This means that under the MPEG standard, a closed GOP structure using acompression method that does not reference any frames outside theinterleave unit must be used. If this method is not used, it is notpossible to seamless connect and reproduce interleave units fromdifferent angles. By using this VOB structure and interleave unitalignment, however, contiguous reproduction is possible time-wise evenif the angle is changed.

The number of interleave units in the multi-angle scene period isdetermined by the number of interleave units in the other angles thatcan be arrayed within the jumpable distance after an interleave unit isread. Regarding the arrangement of the interleaved units in each angle,the interleave units reproduced first in each angle are arrayed in theangle sequence, and are subsequently followed by the interleave unitsreproduced next in each angle being arrayed in the angle sequence. Thus,if the number of angles is M (where M is a natural number, and 1≦M≦9),the m-th angle is angle #m (where m is a natural number, and 1≦m≦M), thenumber of interleave units is N (where N is a natural number greaterthan or equal to 1), and the n-th interleave unit in a VOB is interleaveunit #n (where n is a natural number, and 1≦n≦N), the interleave unitsequence is angle #1 interleave unit #1, angle #2 interleave unit #1,angle #3 interleave unit #1, angle #M interleave unit #1, angle #1interleave unit #2, angle #2 interleave unit #2, If the interleave unitlength of each angle is the shortest read time for seamlessly selectedangles where the angle change is seamless, the maximum distance thatmust be jumped when moving between angles is the distance from the firstangle interleave unit in the sequence to the last interleave unit in theinterleave unit sequence of the next angle reproduced within thesequence of angle interleave units reproduced at the same time. Thus, ifthe number of angles is An, the jump distance must satisfy the followingequation 7.

max. angle ILVU length×(An−1)×2≦jumpable distance  [7]

With non-seamless multi-angle switching, each angle must be seamlesslyreproduced, but seamless reproduction is not required when movingbetween angles. Therefore, if the interleave unit length of each angleis the shortest read time, the maximum distance that must be jumped whenmoving between angles is the distance between the interleave units ofeach angle. Thus, if the number of angles is An, the jump distance mustsatisfy the following equation 8.

max. angle ILVU length×(An−1)≦jumpable distance  [8]

The method of managing addresses on the switching unit level betweenmultiple angle data VOB in multi-angle scene periods is described belowwith reference to FIGS. 49 and 50. In FIG. 49 the angle interleave unitA-ILVU is the data switching unit, and the address of another angleinterleave unit A-ILVU is written to the navigation pack NV of eachangle interleave unit A-ILVU. FIG. 49 shows the address descriptionachieving seamless reproduction, i.e., uninterrupted reproduction of theaudio and video data. This addressing method specifically provides forcontrol whereby only the data for the interleave units of the angle tobe reproduced is read into the track buffer when the angle is changed.

FIG. 50 shows an example in which the video object unit VOBU is the dataswitching unit, and the address of another video object unit VOBU iswritten to the navigation pack NV of each video object unit VOBU. Thisaddressing method provides for non-seamless reproduction control wherebyreproduction can be changed as quickly as possible to another angle nearthe time when the angle is changed.

In FIG. 49, each angle interleave unit A-ILVU in the three multi-angledata VOB-B, VOB-C, and VOB-D records as the address of the next angleinterleave unit A-ILVU to be reproduced the address of a chronologicallylater A-ILVU. Note that VOB-B is designated angle #1, VOB-C is angle #2,and VOB-D is angle #3. The multi-angle data VOB-B consists of angleinterleave units A-ILVUb1, A-ILVUb2, and A-ILVUb3. multi-angle dataVOB-C similarly consists of angle interleave units A-ILVUc1, A-ILVUc2,and A-ILVUc3, and multi-angle data VOB-D of angle interleave unitsA-ILVUd1, A-ILVUd2, and A-ILVUd3.

The navigation pack NV of angle interleave unit A-ILVUb1 containsSML_AGL C#1_DSTA pointing to the relative address of the next angleinterleave unit A-ILVUb2 in VOB-B, as shown by line Pb1 b;SML_AGL_C#2_DSTA pointing to the relative address of VOB-C angleinterleave unit A-ILVUc2 synchronized to the same (next) angleinterleave unit A-ILVUb2 as shown by line Pb1 c; and SML_AGL_C#3_DSTApointing to the relative address of the VoB-D angle interleave unitA-ILVUd2 as shown by line Pb1 d.

As shown by lines Pb2 b, Pb2 c, and Pb2 d, the navigation pack NV of thenext angle interleave unit A-ILVUb2 in the same video object VOB-Blikewise contains SML_AGL_C#1_DSTA, SML_AGL_C#2_DSTA, andSML_AGL_C#3_DSTA pointing to the relative address of the next angleinterleave units A-ILVUb3, A-ILVUc3, and A-ILVUd3 in VOB-B, VOB-C, andVOB-D, respectively.

Note that the relative addresses are all expressed as the number ofsectors from the navigation pack NV of the VOBU contained in eachinterleave unit.

Addresses are similarly written to the navigation pack NV of the firstangle interleave unit A-ILVUc1 in VOB-C, i.e., SML_AGL_C#2_DSTA pointingto the relative address of the next angle interleave unit A-ILVUc2 inVOB-C as shown by line Pc1 c; SML_AGL_C#l_DSTA pointing to the relativeaddress of the same (next) angle interleave unit A-ILVUb2 in VOB-B, asshown by line Pc1 b; and SML_AGL_C#3 DSTA pointing to the relativeaddress of the VOB-D angle interleave unit A-ILVUd2 as shown by line Pc1d.

As shown by lines Pc2 c, Pc2 b, and Pc2 d, the navigation pack NV of thenext angle interleave unit A-ILVUc2 in VOB-C likewise contains therelative addresses SML_AGL_C#2_DSTA, SML_AGL_C#1_DSTA, andSML_AGL_C#3_DSTA pointing to the next angle interleave units A-ILVUc3,A-ILVUb3, and A-ILVUd3 in the respective video objects VOB.

Again note that the relative addresses are all expressed as the numberof sectors from the navigation pack NV of the VOBU contained in eachinterleave unit.

Addresses are similarly written to the navigation pack NV of the firstangle interleave unit A-ILVUd1 in VOB-D, i.e., SML_AGL_C#3_DSTA pointingto the relative address of the next angle interleave unit A-ILVUd2 inVOB-D as shown by line Pdld; SML_AGL_C#l_DSTA pointing to the relativeaddress of the same (next) angle interleave unit A-ILVUb2 in VOB-B, asshown by line Pd1 b; and SML_AGL_C#2_DSTA pointing to the relativeaddress of VOB-C angle interleave unit A-ILVUc2 as shown by line Pd1 c.

As shown by lines Pd2 d, Pd2 b, and Pd2 c, the navigation pack NV of thenext angle interleave unit A-ILVUd2 in VOB-D likewise contains therelative addresses SML_AGL_C#3_DSTA, SML_AGL_C#1_DSTA, andSML_AGL_C#2_DSTA pointing to the next angle interleave units A-ILVUd3,A-ILVUb3, and A-ILVUc3 in the respective video objects VOB.

Again note that the relative addresses are all expressed as the numberof sectors from the navigation pack NV of the VOBU contained in eachinterleave unit.

In addition to the addresses SML AGL C#l DSTA—SML_AGL_C#9_DSTA, eachnavigation pack NV also contains various parameter data as previouslydescribed with respect to FIG. 20, and further description thereof isthus omitted for simplicity.

This address information more specifically includes in the navigationpack NV of angle interleave unit A-ILVUb1, for example, the end addressILVU_EA of the angle interleave unit A-ILVUb1 to which the navigationpack NV belongs, and the addresses SML_AGL_C#1_DSTA, SML_AGL_C#2_DSTA,and SML_AGL_C#3_DSTA of the navigation packs NV of the next angleinterleave units A-ILVUb2, A-ILVUc2, A-ILVUd2 that can be reproduced.The navigation pack NV of A-ILVUb2 contains the end address ILVU_EA ofA-ILVUb2, and the addresses SML_AGL C#l_DSTA, SML_AGL_C#2_DSTA, andSML-AGL-C#3-DSTA of the navigation packs NV of the next angle interleaveunits A-ILVUb3, A-ILVUc3, A-ILVUd3 reproduced. The navigation pack NV ofA-ILVUb3, the last interleave unit in the sequence in this example,contains the end address ILVU_EA of A-ILVUb3, and terminationinformation as the address of the navigation pack NV of the next A-ILVUreproduced, e.g., a NULL value or string of all is as the ILVU_EA.

The specifics of the address information written to the other videoobjects VOB-C and VOB-D in this example are the same.

By writing this address information to the navigation packs NV of eachangle interleave unit A-ILVU, it is possible to read ahead the addressof the next A-ILVU to be reproduced in chronological sequence, and istherefore suited to seamless reproduction. Furthermore, because theaddress of the next A-ILVU in each of the other available angles is alsorecorded to each navigation pack NV, the next address of the selectedangle can be easily obtained without giving special consideration towhether the angle is changed or not, and jumping to the next interleaveunit can be controlled by the same control sequence.

By thus recording the relative addresses of each A-ILVU that can beselected from each angle, and constructing the encoded video streamcontained in each A-ILVU from closed GOP, seamless reproduction withoutvideo disruption can be achieved when the viewing angle is changed.

The audio data can also be seamlessly reproduced if the same audio isrecorded for each angle, if the audio is complete within each ILVU, orif discrete audio data is recorded. Moreover, if identical audio data isrecorded to each interleaved unit ILVU, the listener will not even beable to discern that the audio track has changed if the audio isseamlessly reproduced across angle changes.

A data structure enabling non-seamless reproduction of angle changes,i.e., seamless data reproduction permitting perceptible breaks in thecontent of the reproduced information, is described below with referenceto FIG. 50.

It is assumed in FIG. 50 that multi-angle data VOB-B comprises threevideo object units VOBUb1, VOBUb2, and VOBUb3. Multi-angle data VOB-Csimilarly comprises three video object units VOBUc1, VOBUc2, and VOBUc3,and VOB-D comprises three video object units VOBUd1, VOBUd2, and VOBUd3.As in the case shown in FIG. 49, the navigation pack NV of each videoobject unit VOBU contains the end pack address VOBU_EA of each VOBU.Note that this end pack address VOBU_EA is the address of a navigationpack NV in a VOBU comprising a navigation pack NV and one or more otherpacks. In this example, however, the NSML_AGL_C#_DSTA address written tothe navigation pack NV of each VOBU does not describe a chronologicallylater VOBU address, but the address of a VOBU in a different angle witha reproduction time preceding the time the angle is changed.

In other words, addresses NSML_AGL_C#1_DSTA to NSML_AGL_C#9_DSTA to VOBUin other angles synchronized to the current VOBU are recorded. As above,#1-#9 represent different angle numbers. For fields in which an angle ofthe corresponding number does not exist, a value, e.g., 0, indicatingthat the angle does not exist is recorded. Thus, the navigation pack NVof video object unit VOBUb1 of multi-angle data VOB-B contains NSMLAGL_C#2_DSTA and NSML_AGL C#3_DSTA, the relative addresses of thesynchronized VOBUc1 and VOBUd1 in VOB-C and VOB-D as shown by lines Pb1c′ and Pb1 d′.

The navigation pack NV of video object unit VOBUb2 similarly contains asshown by lines Pb2 c′ and Pb2 d′ the relative addresses NSML AGLC#2_DSTA and NSML_AGL_C#3_DSTA of the synchronized VOBUc2 and VOBUd2.The navigation pack NV of video object unit VOBUb3 similarly contains asshown by lines Pb3 c′ and Pb3 d′ the relative addresses NSML AGLC#2_DSTA and NSML_AGL C#3_DSTA of the synchronized VOBUc3 and VOBUd3.

The navigation packs NV of video object units VOBUc1, VOBUc2, and VOBUc3of VOB-C similarly contain the relative addresses NSML_AGL_C#1_DSTA andNSML_AGL_C#3_DSTA of the respectively synchronized VOBU as shown bylines Pc1 b′, Pc1 d′, Pc2 b′, Pc2 d′, Pc3 b′, and Pc3 d′.

The navigation packs NV of video object units VOBUd1, VOBUd2, and VOBUd3of VOB-D likewise contain the relative addresses NSML_AGL_C#l_DSTA andNSML_AGL_C#2_DSTA of the respectively synchronized VOBU as shown bylines Pd1 b′, Pd1 c′, Pd2 b′, Pd2 c′, Pd3 b′, and Pd3 c′.

The angle selection address information NSML_AGL_C#4_DSTA to NSML_AGLC#9_DSTA for non-existent angles #4-#9 in this example record a valueindicating that corresponding angles do not exist, e.g., a 0 value.

During reproduction of angle data with this data structure, the DVDdecoder interrupts reproduction of the angle VOBU data currently beingreproduced when the angle is changed, then reads and begins reproducingthe VOBU data for the selected angle.

Note that while there appears to be a time offset between theinterleaved units of VOB-C relative to VOB-B and VOB-D in FIG. 50, thisis merely to facilitate easier understanding of the address descriptionswritten to the respective navigation packs NV of each VOB using the linearrows as shown. There is, in fact, no time shifting between therespective interleaved video objects VOB, which are aligned as shown inFIG. 49.

The data structure shown in FIG. 50 thus contains as pointers to thenext VOBU to be reproduced addresses to another VOBU that shouldnormally be reproduced either simultaneously with or chronologicallybefore the VOBU containing the address information. Therefore, when theangle is changed, reproduction is continued from a scene at a past pointin time. This method of encoding the address information is thuspreferable when seamless angle switching not required, i.e., fornon-seamless information reproduction in which contiguity is notrequired in the reproduced information.

Flow Chart: Encoder

The encoding information table generated by the encoding systemcontroller 200 from information extracted from the scenario data St7 isdescribed below referring to FIG. 27.

The encoding information table contains VOB set data streams containingplural VOB corresponding to the scene periods beginning and ending atthe scene branching and connecting points, and VOB data streamscorresponding to each scene. These VOB set data streams shown in FIG. 27are the encoding information tables generated at step #100 in FIG. 51 bythe encoding system controller 200 for creating the DVD multimediastream based on the user-defined title content.

The user-defined scenario contains branching points from common scenesto plural scenes, or connection points to other common scenes. The VOBcorresponding to the scene period delimited by these branching andconnecting points is a VOB set, and the data generated to encode a VOBset is the VOB set data stream. The title number specified by the VOBset data stream is the title number TITLE_NO of the VOB set data stream.

The VOB Set data structure in FIG. 27 shows the data content forencoding one VOB set in the VOB set data stream, and comprises: the VOBset number VOBS_NO, the VOB number VOB_NO in the VOB set, the precedingVOB seamless connection flag VOB_Fsb, the following VOB seamlessconnection flag VOB_Fsf, the multi-scene flag VOB_Fp, the interleaveflag VOB_Fi, the multi-angle flag VOB_Fm, the multi-angle seamlessswitching flag VOB_FsV, the maximum bit rate of the interleaved VOBILV_BR, the number of interleaved VOB divisions ILV_DIV, and the minimuminterleaved unit presentation time ILVU_MT.

The VOB set number VOBS_NO is a sequential number identifying the VOBset and the position of the VOB set in the reproduction sequence of thetitle scenario.

The VOB number VOB_NO is a sequential number identifying the VOB and theposition of the VOB in the reproduction sequence of the title scenario.

The preceding VOB seamless connection flag VOB_Fsb indicates whether aseamless connection with the preceding VOB is required for scenarioreproduction.

The following VOB seamless connection flag VOB_Fsf indicates whetherthere is a seamless connection with the following VOB during scenarioreproduction.

The multi-scene flag VOB_Fp identifies whether the VOB set comprisesplural video objects VOB.

The interleave flag VOB_Fi identifies whether the VOB in the VOB set areinterleaved.

The multi-angle flag VOB_Fm identifies whether the VOB set is amulti-angle set.

The multi-angle seamless switching flag VOB_FsV identifies whether anglechanges within the multi-angle scene period are seamless or not.

The maximum bit rate of the interleaved VOB ILV_BR defines the maximumbit rate of the interleaved VOBs.

The number of interleaved VOB divisions ILV_DIV identifies the number ofinterleave units in the interleaved VOB.

The minimum interleave unit presentation time ILVU_MT defines the timethat can be reproduced when the bit rate of the smallest interleave unitat which a track buffer data underflow state does not occur is themaximum bit rate of the interleaved VOB ILV_BR during interleaved blockreproduction.

The encoding information table for each VOB generated by the encodingsystem controller 200 based on the scenario data St7 is described belowreferring to FIG. 28. The VOB encoding parameters described below andsupplied to the video encoder 300, audio encoder 700, and system encoder900 for stream encoding are produced based on this encoding informationtable.

The VOB data streams shown in FIG. 28 are the encoding informationtables generated at step #100 in FIG. 51 by the encoding systemcontroller 200 for creating the DVD multimedia stream based on theuser-defined title content.

The encoding unit is the video object VOB, and the data generated toencode each video object VOB is the VOB data stream. For example, a VOBset comprising three angle scenes comprises three video objects VOB. Thedata structure shown in FIG. 28 shows the content of the data forencoding one VOB in the VOB data stream.

The VOB data structure contains the video material start time VOB_VST,the video material end time VOB VEND, the video signal type VOB_V_KIND,the video encoding bit rate V_BR, the audio material start time VOB AST,the audio material end time VOB_AEND, the audio coding methodVOB_A_KIND, and the audio encoding bit rate A_BR.

The video material start time VOB_VST is the video encoding start timecorresponding to the time of the video signal.

The video material end time VOB_VEND is the video encoding end timecorresponding to the time of the video signal.

The video material type VOB_V_KIND identifies whether the encodedmaterial is in the NTSC or PAL format, for example, or is photographicmaterial (a movie, for example) converted to a television broadcastformat (so-called telecine conversion).

The video encoding bit rate V_BR is the bit rate at which the videosignal is encoded.

The audio material start time VOB_AST is the audio encoding start timecorresponding to the time of the audio signal.

The audio material end time VOB_AEND is the audio encoding end timecorresponding to the time of the audio signal.

The audio coding method VOB_A_KIND identifies the audio encoding methodas AC-3, MPEG, or linear PCM, for example.

The audio encoding bit rate A_BR is the bit rate at which the audiosignal is encoded.

The encoding parameters used by the video encoder 300, sub-pictureencoder 500, and audio encoder 700, and system encoder 900 for VOBencoding are shown in FIG. 29. The encoding parameters include: the VOBnumber VOB_NO, video encode start time V_STTM, video encode end timeV_ENDTM, the video encode mode V_ENCMD, the video encode bit rateV_RATE, the maximum video encode bit rate V_MRATE, the GOP structurefixing flag GOP_Fxflag, the video encode GOP structure GOPST, theinitial video encode data V_INTST, the last video encode data V_ENDST,the audio encode start time A_STTM, the audio encode end time A_ENDTM,the audio encode bit rate A_RATE, the audio encode method A_ENCMD, theaudio start gap A_STGAP, the audio end gap A_ENDGAP, the preceding VOBnumber B_VOB_NO, and the following VOB number F_VOB_NO.

The VOB number VOB_NO is a sequential number identifying the VOB and theposition of the VOB in the reproduction sequence of the title scenario.

The video encode start time V_STTM is the start time of video materialencoding.

The video encode end time V_ENDTM is the end time of video materialencoding.

The video encode mode V_ENCMD is an encoding mode for declaring whetherreverse telecine conversion shall be accomplished during video encodingto enable efficient coding when the video material is telecine convertedmaterial.

The video encode bit rate V_RATE is the average bit rate of videoencoding.

The maximum video encode bit rate V_MRATE is the maximum bit rate ofvideo encoding.

The GOP structure fixing flag GOP_Fxflag specifies whether encoding isaccomplished without changing the GOP structure in the middle of thevideo encoding process. This is a useful parameter for declaring whetherseamless switch is enabled in a multi-angle scene period.

The video encode GOP structure GOPST is the GOP structure data fromencoding.

The initial video encode data V_INTST sets the initial value of the VBVbuffer (decoder buffer) at the start of video encoding, and isreferenced during video decoding to initialize the decoding buffer. Thisis a useful parameter for declaring seamless reproduction with thepreceding encoded video stream.

The last video encode data V_ENDST sets the end value of the VBV buffer(decoder buffer) at the end of video encoding, and is referenced duringvideo decoding to initialize the decoding buffer. This is a usefulparameter for declaring seamless reproduction with the preceding encodedvideo stream.

The audio encode start time A_STTM is the start time of audio materialencoding.

The audio encode end time A_ENDTM is the end time of audio materialencoding.

The audio encode bit rate A_RATE is the bit rate used for audioencoding.

The audio encode method A_ENCMD identifies the audio encoding method asAC-3, MPEG, or linear PCM, for example.

The audio start gap A_STGAP is the time offset between the start of theaudio and video presentation at the beginning of a VOB. This is a usefulparameter for declaring seamless reproduction with the preceding encodedsystem stream.

The audio end gap A_ENDGAP is the time offset between the end of theaudio and video presentation at the end of a VOB. This is a usefulparameter for declaring seamless reproduction with the preceding encodedsystem stream.

The preceding VOB number B_VOB_NO is the VOB_NO of the preceding VOBwhen there is a seamlessly connected preceding VOB.

The following VOB number F_VOB_NO is the VOB_NO of the following VOBwhen there is a seamlessly connected following VOB.

The operation of a DVD encoder ECD according to the present invention isdescribed below with reference to the flow chart in FIG. 51. Note thatthe steps shown with a double line are subroutines. It should be obviousthat while the operation described below relates specifically in thiscase to the DVD encoder ECD of the present invention, the operationdescribed also applies to an authoring encoder EC.

At step #100, the user inputs the editing commands according to theuser-defined scenario while confirming the content of the multimediasource data streams St1, St2, and St3.

At step #200, the scenario editor 100 generates the scenario data St7containing the above edit command information according to the user'sediting instructions.

When generating the scenario data St7 in step #200, the user editingcommands related to multi-angle and parental lock multi-scene periods inwhich interleaving is presumed must be input to satisfy the followingconditions.

First, the VOB maximum bit rate must be set to assure sufficient imagequality, and the track buffer capacity, jump performance, jump time, andjump distance of the DVD decoder DCD used as the reproduction apparatusof the DVD encoded data must be determined. Based on these values, thereproduction time of the shortest interleaved unit is obtained fromequations 3 and 4. Based on the reproduction time of each scene in themulti-scene period, it must then be determined whether equations 5 and 6are satisfied. If equations 5 and 6 are not satisfied, the user mustchange the edit commands until equations 5 and 6 are satisfied by, forexample, connecting part of the following scene to each scene in themulti-scene period.

When multi-angle edit commands are used, equation 7 must be satisfiedfor seamless switching, and edit commands matching the audioreproduction time with the reproduction time of each scene in each anglemust be entered. If non-seamless switching is used, the user must entercommands to satisfy equation 8.

At step #300, the encoding system controller 200 first determineswhether the target scene is to be seamlessly connected to the precedingscene based on the scenario data St7.

Note that when the preceding scene period is a multi-scene periodcomprising plural scenes but the presently selected target scene is acommon scene (not in a multi-scene period), a seamless connection refersto seamlessly connecting the target scene with any one of the scenescontained in the preceding multi-scene period. When the target scene isa multi-scene period, a seamless connection still refers to seamlesslyconnecting the target scene with any one of the scenes from the samemulti-scene period.

If step #300 returns NO, i.e., a non-seamless connection is valid, theprocedure moves to step #400.

At step #400, the encoding system controller 200 resets the precedingVOB seamless connection flag VOB_Fsb indicating whether there is aseamless connection between the target and preceding scenes. Theprocedure then moves to step #600.

On the other hand, if step #300 returns YES, i.e., there is a seamlessconnection to the preceding scene, the procedure moves to step #500.

At step #500 the encoding system controller 200 sets the preceding VOBseamless connection flag VOB_Fsb. The procedure then moves to step #600.

At step #600 the encoding system controller 200 determines whether thereis a seamless connection between the target and following scenes basedon scenario data St7. If step #600 returns NO, i.e., a non-seamlessconnection is valid, the procedure moves to step #700.

At step #700, the encoding system controller 200 resets the followingVOB seamless connection flag VOB_Fsf indicating whether there is aseamless connection with the following scene. The procedure then movesto step #900.

However, if step #600 returns YES, i.e., there is a seamless connectionto the following scene, the procedure moves to step #800.

At-step #800 the encoding system controller 200 sets the following VOBseamless connection flag VOB_Fsf. The procedure then moves to step #900.

At step #900 the encoding system controller 200 determines whether thereis more than connection target scene, i.e., whether a multi-scene periodis selected, based on the scenario data St7. As previously described,there are two possible control methods in multi-scene periods: parentallock control whereby only one of plural possible reproduction paths thatcan be constructed from the scenes in the multi-scene period isreproduced, and multi-angle control whereby the reproduction path can beswitched within the multi-scene period to present different viewingangles.

If step #900 returns NO, i.e., there are not multiple scenes, theprocedure moves to step #1000.

At step #1000 the multi-scene flag VOB_Fp identifying whether the VOBset comprises plural video objects VOB (a multi-scene period isselected) is reset, and the procedure moves to step #1800 for encodeparameter production. This encode parameter production subroutine isdescribed below.

However, if step #900 returns YES, there is a multi-scene connection,the procedure moves to step #1100.

At step #1100, the multi-scene flag VOB_Fp is set, and the proceduremoves to step #1200 whereat it is judged whether a multi-angleconnection is selected, or not.

At step #1200 it is determined whether a change is made between pluralscenes in the multi-scene period, i.e., whether a multi-angle sceneperiod is selected. If step #1200 returns NO, i.e., no scene change isallowed in the multi-scene period as parental lock control reproducingonly one reproduction path has been selected, the procedure moves tostep #1300.

At step #1300 the multi-angle flag VOB_Fm identifying whether the targetconnection scene is a multi-angle scene is reset, and the proceduremoves to step #1302.

At step #1302 it is determined whether either the preceding VOB seamlessconnection flag VOB_Fsb or following VOB seamless connection flagVOB_Fsf is set. If step #1302 returns YES, i.e., the target connectionscene seamlessly connects to the preceding, the following, or both thepreceding and following scenes, the procedure moves to step #1304.

At step #1304 the interleave flag VOB_Fi identifying whether the VOB,the encoded data of the target scene, is interleaved is set. Theprocedure then moves to step #1800.

However, if step #1302 returns NO, i.e., the target connection scenedoes not seamlessly connect to the preceding or following scene, theprocedure moves to step #1306.

At step #1306 the interleave flag VOB_Fi is reset, and the proceduremoves to step #1800.

If step #1200 returns YES, however, i. e., there is a multi-angleconnection, the procedure moves to step #1400.

At step #1400, the multi-angle flag VOB_Fm and interleave flag VOB_Fiare set, and the procedure moves to step #1500.

At step #1500 the encoding system controller 200 determines whether theaudio and video can be seamlessly switched in a multi-angle sceneperiod, i.e., at a reproduction unit smaller than the VOB, based on thescenario data St7. If step #1500 returns NO, i.e., non-seamlessswitching occurs, the procedure moves to step #1600.

At step #1600 the multi-angle seamless switching flag VOB_FsV indicatingwhether angle changes within the multi-angle scene period are seamlessor not is reset, and the procedure moves to step #1800.

However, if step #1500 returns YES, i.e., seamless switching occurs, theprocedure moves to step #1700.

At step #1700 the multi-angle seamless switching flag VOB_FsV is set,and the procedure moves to step #1800.

Therefore, as shown by the flow chart in FIG. 51, encode parameterproduction (step #1800) is only begun after the editing information isdetected from the above flag settings in the scenario data St7reflecting the user-defined editing instructions.

Based on the user-defined editing instructions detected from the aboveflag settings in the scenario data St7, information is added to theencoding information tables for the VOB Set units and VOB units as shownin FIGS. 27 and 28 to encode the source streams, and the encodingparameters of the VOB data units shown in FIG. 29 are produced, in step#1800. The procedure then moves to step #1900 for audio and videoencoding.

The encode parameter production steps (step #1800) are described ingreater detail below referring to FIGS. 52, 53, 54, and 55.

Based on the encode parameters produced in step #1800, the video dataand audio data are encoded in step #1900, and the procedure moves tostep #2000.

Note that the sub-picture data is normally inserted during videoreproduction on an as-needed basis, and contiguity with the precedingand following scenes is therefore not usually necessary. Moreover, thesub-picture data is normally video information for one frame, and unlikeaudio and video data having an extended time-base, sub-picture data isusually static, and is not normally presented continuously. Because thepresent invention relates specifically to seamless and non-seamlesscontiguous reproduction as described above, description of sub-picturedata encoding is omitted herein for simplicity.

Step #2000 is the last step in a loop comprising steps #300 to step#2000, and causes this loop to be repeated as many times as there areVOB Sets. This loop formats the program chain VTS_PGC#i to contain thereproduction sequence and other reproduction information for each VOB inthe title (FIG. 16) in the program chain data structure, interleaves theVOB in the multi-scene periods, and completes the VOB Set data streamand VOB data stream needed for system stream encoding. The procedurethen moves to step #2100.

At step #2100 the VOB Set data stream is completed as the encodinginformation table by adding the total number of VOB Sets VOBS_NUMobtained as a result of the loop through step #2000 to the VOB Set datastream, and setting the number of titles TITLE_NO defining the number ofscenario reproduction paths in the scenario data St7. The procedure thenmoves to step #2200.

System stream encoding producing the VOB (VOB#i) data in the VTS titleVOBS (VTSTT_VOBS) (FIG. 16) is accomplished in step #2200 based on theencoded video stream and encoded audio stream output from step #1900,and the encode parameters in FIG. 29. The procedure then moves to step#2300.

At step #2300 the VTS information VTSI, VTSI management table VTSI_MAT,VTSPGC information table VTS_PGCIT, and the program chain informationVTS_PGCI#i controlling the VOB data reproduction sequence shown in FIG.16 are produced, and formatting to, for example, interleave the VOBcontained in the multi-scene periods, is accomplished. The specificsteps executed in this formatting operation are described below withreference to FIGS. 56, 57, 58, 59, and 60.

The encode parameter production subroutine shown as step #1800 in FIG.51B is described next using FIGS. 52, 53, and 54 using by way of examplethe operation generating the encode parameters for multi-angle control.

Starting from FIG. 52, the process for generating the encode parametersof a non-seamless switching stream with multi-angle control is describedfirst. This stream is generated when step #1500 in FIG. 51 returns NOand the following flags are set as shown: VOB_Fsb=1 or VOB_Fsf=1, VOB_Fp1, VOB_Fi=1, VOB_Fm=1, and VOB_FsV=0. The following operation producesthe encoding information tables shown in FIG. 27 and FIG. 28, and theencode parameters shown in FIG. 29.

At step #1812, the scenario reproduction sequence (path) contained inthe scenario data St7 is extracted, the VOB Set number VOBS_NO is set,and the VOB number VOB_NO is set for one or more VOB in the VOB Set.

At step #1814 the maximum bit rate ILV_BR of the interleaved VOB isextracted from the scenario data St7, and the maximum video encode bitrate V_MRATE from the encode parameters is set based on the interleaveflag VOB_Fi setting (=1).

At step #1816, the minimum interleaved unit presentation time ILVU_MT isextracted from the scenario data St7.

At step #1818, the video encode GOP structure GOPST values N=15 and M=3are set, and the GOP structure fixing flag GOP_Fxflag is set (=1), basedon the multi-scene flag VOB_Fp setting (=1).

Step #1820 is the common VOB data setting routine, which is describedbelow referring to the flow chart in FIG. 53. This common VOB datasetting routine produces the encoding information tables shown in FIGS.27 and 28, and the encode parameters shown in FIG. 29.

At step #1822 the video material start time VOB_VST and video materialend time VOB_VEND are extracted for each VOB, and the video encode starttime V_STTM and video encode end time V_ENDTM are used as video encodingparameters.

At step #1824 the audio material start time VOB_AST of each VOB isextracted from the scenario data St7, and the audio encode start timeA_STTM is set as an audio encoding parameter.

At step #1826 the audio material end time VOB_AEND is extracted for eachVOB from the scenario data St7, and at a time not exceeding the VOB_AENDtime. This time extracted at an audio access unit (AAU) is set as theaudio encode end time A_ENDTM which is an audio encoding parameter. Notethat the audio access unit AAU is determined by the audio encodingmethod.

At step #1828 the audio start gap A_STGAP obtained from the differencebetween the video encode start time V_STTM and the audio encode starttime A_STTM is defined as a system encode parameter.

At step #1830 the audio end gap A_ENDGAP obtained from the differencebetween the video encode end time V_ENDTM and the audio encode end timeA_ENDTM is defined as a system encode parameter.

At step #1832 the video encoding bit rate V_BR is extracted from thescenario data St7, and the video encode bit rate V RATE, which is theaverage bit rate of video encoding, is set as a video encodingparameter.

At step #1834 the audio encoding bit rate A_BR is extracted from thescenario data St7, and the audio encode bit rate A_RATE is set as anaudio encoding parameter.

At step #1836 the video material type VOB_V_KIND is extracted from thescenario data St7. If the material is a film type, i.e., a movieconverted to television broadcast format (so-called telecineconversion), reverse telecine conversion is set for the video encodemode V_ENCMD, and defined as a video encoding parameter.

At step #1838 the audio coding method VOB_A_KIND is extracted from thescenario data St7, and the encoding method is set as the audio encodemethod A_ENCMD and set as an audio encoding parameter.

At step #1840 the initial video encode data V_INTST sets the initialvalue of the VBV buffer to a value less than the VBV buffer end valueset by the last video encode data V_ENDST, and defined as a videoencoding parameter.

At step #1842 the VOB number VOB_NO of the preceding connection is setto the preceding VOB number B_VOB_NO based on the setting (=1) of thepreceding VOB seamless connection flag VOB_Fsb, and set as a systemencode parameter.

At step #1844 the VOB number VOB_NO of the following connection is setto the following VOB number F VOB_NO based on the setting (=1) of thefollowing VOB seamless connection flag VOB_Fsf, and set as a systemencode parameter.

The encoding information table and encode parameters are thus generatedfor a multi-angle VOB Set with non-seamless multi-angle switchingcontrol enabled.

The process for generating the encode parameters of a seamless switchingstream with multi-angle control is described below with reference toFIG. 54. This stream is generated when step #1500 in FIG. 51 returns YESand the following flags are set as shown: VOB Fsb =1 or VOB_Fsf 1,VOB_Fp=1, VOB_Fi=1, VOB_Fm=1, and VOB_FsV=1. The following operationproduces the encoding information tables shown in FIG. 27 and FIG. 28,and the encode parameters shown in FIG. 29.

The following operation produces the encoding information tables shownin FIG. 27 and FIG. 28, and the encode parameters shown in FIG. 29.

At step #1850, the scenario reproduction sequence (path) contained inthe scenario data St7 is extracted, the VOB Set number VOBS_NO is set,and the VOB number VOB_NO is set for one or more VOB in the VOB Set.

At step #1852 the maximum bit rate ILV_BR of the interleaved VOB isextracted from the scenario data St7, and the maximum video encode bitrate V_MRATE from the encode parameters is set based on the interleaveflag VOB_Fi setting (=1).

At step #1854, the minimum interleaved unit presentation time ILVU_MT isextracted from the scenario data St7.

At step #1856, the video encode GOP structure GOPST values N=15 and M=3are set, and the GOP structure fixing flag GOP_Fxflag is set (=1), basedon the multi-scene flag VOB_Fp setting (=1).

At step #1858, the video encode GOP GOPST is set to “closed GOP” basedon the multi-angle seamless switching flag VOB_FsV setting (=1), and thevideo encoding parameters are thus defined.

Step #1860 is the common VOB data setting routine, which is as describedreferring to the flow chart in FIG. 52. Further description thereof isthus omitted here.

The encode parameters of a seamless switching stream with multi-anglecontrol are thus defined for a VOB Set with multi-angle control asdescribed above.

The process for generating the encode parameters for a system stream inwhich parental lock control is implemented is described below withreference to FIG. 55. This stream is generated when step #1200 in FIG.51 returns NO and step #1304 returns YES, i.e., the following flags areset as shown: VOB_Fsb=1 or VOB_Fsf=1, VOB_Fp=1, VOB_Fi=1, VOB_Fm=0. Thefollowing operation produces the encoding information tables shown inFIG. 27 and FIG. 28, and the encode parameters shown in FIG. 29.

At step #1870, the scenario reproduction sequence (path) contained inthe scenario data St7 is extracted, the VOB Set number VOBS_NO is set,and the VOB number VOB_NO is set for one or more VOB in the VOB Set.

At step #1872 the maximum bit rate ILV_BR of the interleaved VOB isextracted from the scenario data St7, and the maximum video encode bitrate V_MRATE from the encode parameters is set based on the interleaveflag VOB_Fi setting (=1).

At step #1872 the number of interleaved VOB divisions ILV_DIV isextracted from the scenario data St7.

Step #1876 is the common VOB data setting routine, which is as describedreferring to the flow chart in FIG. 52. Further description thereof isthus omitted here.

The encode parameters of a system stream in which parental lock controlis implemented are thus defined for a VOB Set with multi-scene selectioncontrol enabled as described above.

The process for generating the encode parameters for a system streamcontaining a single scene is described below with reference to FIG. 61.This stream is generated when step #900 in FIG. 51 returns NO, i.e.,when VOB_Fp=0. The following operation produces the encoding informationtables shown in FIG. 27 and FIG. 28, and the encode parameters shown inFIG. 29.

At step #1880, the scenario reproduction sequence (path) contained inthe scenario data St7 is extracted, the VOB Set number VOBS_NO is set,and the VOB number VOB_NO is set for one or more VOB in the VOB Set.

At step #1882 the maximum bit rate ILV_BR of the interleaved VOB isextracted from the scenario data St7, and the maximum video encode bitrate V_MRATE from the encode parameters is set based on the interleaveflag VOB_Fi setting (=1).

Step #1884 is the common VOB data setting routine, which is as describedreferring to the flow chart in FIG. 52. Further description thereof isthus omitted here.

These flow charts for defining the encoding information table and encodeparameters thus generate the parameters for DVD video, audio, and systemstream encoding by the DVD formatter.

The operation of the subroutine executed by the DVD formatter shown asstep #2300 in FIG. S5B is described next with reference to FIGS. 56, 57,58, 59, and 60. This formatter subroutine generates the DVD multimediabitstream.

The operation of the DVD encoder ECD 1100 according to the presentinvention is described with reference to the flow chart in FIG. 56. Notethat those steps shown in FIG. 56 with a double line are subroutines.

At step #2310 the program chain information VTS_PGCI is set to the VTSImanagement table VTSI_MAT for the number of titles TITLE_NUM based onthe number of titles TITLE_NUM in the VOB Set data stream.

At step #2312 it is determined whether multi-scene selection control isenabled based on the multi-scene flag VOB_Fp in the VOB Set data stream.If step #2312 returns NO, i.e., multi-scene control is not enabled, theprocedure moves to step #2114.

At step #2314 the operation for coding a single scene (VOB) executed bythe formatter 1100 of the authoring encoder EC shown in FIG. 25 isaccomplished. This routine is described later.

If step #2312 returns YES, i.e., multi-scene control is enabled, theprocedure moves to step #2116.

At step #2316 it is determined whether the information is to beinterleaved or not based on the interleave flag VOB_Fi state in the VOBSet data stream. If step #2316 returns NO, i.e., the information is notto be interleaved, the procedure moves to step #2314. If step #2316returns YES, i.e., the information is to be interleaved, the proceduremoves to step #2318.

At step #2318 it is determined whether multi-angle control is to beimplemented based on the multi-angle flag VOB_Fm in the VOB Set datastream. If step #2318 returns NO, the parental lock control routine instep #2320 is executed. If step #2318 returns YES, the procedure movesto step #2322.

At step #2320 the operation for formatting the VOB Set for parental lockcontrol is executed. This subroutine is shown in FIG. 59 and describedbelow.

At step #2322 it is determined whether multi-angle seamless switching isrequired based on the multi-angle seamless switching flag VOB_FsV. Ifmulti-angle switching is accomplished without seamless switching, i.e.,with non-seamless switching and step #2322 returns NO, the proceduremoves to step #2326.

The multi-angle non-seamless switching control routine executed in step#2326 by the formatter 1100 of the authoring encoder EC in FIG. 25 isdescribed later with reference to FIG. 57.

If multi-angle switching is accomplished with seamless switchingcontrol, i.e., step #2322 returns YES, the procedure moves to step#2324.

The multi-angle seamless switching control routine executed in step#2324 by the formatter 1100 of the authoring encoder EC in FIG. 25 isdescribed later with reference to FIG. 58.

The cell playback information (PCG information entries C_PBI) of the VTSinformation VTSI set as previously described is then recorded.

At step #2330 it is determined whether all VOB Sets declared by the VOBSet number VOBS_NUM have been processed by the formatter. If NO, controlloops back to step #2312, and the process runs again. If YES, all setshave been formatted, the procedure terminates.

Referring to FIG. 57, the multi-angle non-seamless switching controlroutine executed in step #2326 when step #2322, FIG. 56, returns NO isdescribed. This routine defines the interleaved arrangement of themultimedia bitstream MBS, the content of the cell playback information(C_PBI#i) shown in FIG. 16, and the information stored to the navigationpack NV shown in FIG. 20, in the generated DVD multimedia bitstream MBS.

At step #2340 based on the multi-angle flag VOB_Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block mode CBM (FIG. 16) of the cell playbackinformation blocks C_PBI #i containing the VOB control information foreach scene is declared according to the position of the angle data. Forexample, the cell block mode CBM of the MA1 cell (FIG. 23) is declaredas 01b to indicate the beginning of the cell block, the CBM of MA2 isdeclared as lob to indicate a cell between the first and last cells inthe block, and the CBM of MA3 is declared as 11 b to indicate the end ofthe cell block.

At step #2342 based on the multi-angle flag VOB_Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block type CBT (FIG. 16) of the cell playbackinformation blocks C_PBI #i containing the VOB control information foreach scene is declared as 01 b to indicate an “angle.”

At step #2344 the seamless playback flag SPF (FIG. 16) is set to 1 inthe cell playback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

At step #2346 the STC resetting flag STCDF is set to 1 in the cellplayback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

At step #2348 the interleaved allocation flag IAF (FIG. 16) is set to 1in the cell playback information blocks C_PBI #i containing the VOBcontrol information for each scene based on the multi-angle seamlessswitching flag VOB_FsV state, which is set to 1 to indicate interleavingis required.

At step #2350 the location of the navigation pack NV (relative sectornumber from the VOB beginning) is detected from the title editing unit(VOB below) obtained from the system encoder 900 in FIG. 25, thenavigation pack NV is detected based on the minimum interleaved unitpresentation time ILVU_MT information (a formatter parameter obtained instep #1816, FIG. 51), the location of the VOBU expressed as the numberof sectors from the VOB beginning, for example, is thus obtained, andthe title editing unit VOB is divided into interleave units using VOBUunits.

For example, if in this example the minimum interleaved unitpresentation time ILVU_MT is 2 sec and the presentation time of one VOBUis 0.5 sec., then the VOB is divided into interleave units of 4 VOBUeach. Note that this allocation operation is applied to the VOBconstituting each multi-scene data unit.

At step #2352 the interleave units of each VOB obtained from step #2350are arranged in the cell block mode CBM sequence (cell block beginning,middle, and end cells) written as the VOB control information foreachscene in step #2340 to form the interleaved blocks as shown in FIG.37 or 38. The interleaved blocks are then added to the VTS title VOBS(VTSTT_VOBS). Using the cell block mode CBM declarations above, forexample, the angle data MA1, MA2, and MA3 (FIG. 23) are arranged in thatsequence.

At step #2354 the relative sector number from the VOBU start is writtento the VOB end pack address VOBU_EA (FIG. 20) in the navigation pack NVof each VOBU based on the VOBU position information obtained in step#2350.

At step #2356 the first cell VOBU start address C_FVOBU_SA and the lastcell VOBU start address C_LVOBU_SA expressed as the number of sectorsfrom the beginning of the VTS title VOBS (VTSTT_VOBS) are written as theaddresses of the navigation packs NV of the first and last VOBU in eachcell based on the VTS title VOBS (VTSTT_VOBS) data obtained in step#2352.

The angle #i VOBU start address NSML_AGL_C1_DSTA —NSML_AGL_C9_DSTA ofthe non-seamless angle information NSML_AGLI (FIG. 20) in the navigationpack NV of each VOBU is written at step #2358. This address is expressedas the relative sector number inside the data of the interleaved blocksformed in step #2352, and declares the address information (FIG. 50) ofthe navigation pack NV contained in the VOBU of all angle scenes nearthe presentation start time of the VOBU being processed.

At step #2360 “7FFFFFFFh” is written to the angle #i VOBU start addressNSML_AGL_C1_DSTA_NSML_AGL_C9_DSTA of the non-seamless angle informationNSML_AGLI (FIG. 20) in the navigation pack NV of each VOBU if the VOBUbeing processed is the last VOBU of each scene in the multi-sceneperiod.

This routine thus formats the interleaved blocks for multi-anglenon-seamless switching control in the multi-scene period, and formatsthe cell control information as the reproduction control information forthose multiple scenes.

Referring to FIG. 58, the multi-angle seamless switching control routineexecuted in step #2324 when step #2322, FIG. 56, returns YES isdescribed. This routine defines the interleaved arrangement of themultimedia bitstream MBS, the content of the cell playback information(C_PBI#i) shown in FIG. 16, and the information stored to the navigationpack NV shown in FIG. 20, in the generated DVD multimedia bitstream MBS.

At step #2370 based on the multi-angle flag VOB_Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block mode CBM (FIG. 16) of the cell playbackinformation blocks C_PBI #i containing the VOB control information foreach scene is declared according to the position of the angle data. Forexample, the cell block mode CBM of the MA1 cell (FIG. 23) is declaredas 01 b to indicate the beginning of the cell block, the CBM of MA2 isdeclared as 10 b to indicate a cell between the first and last cells inthe block, and the CBM of MA3 is declared as 11 b to indicate the end ofthe cell block.

At step #2372 based on the multi-angle flag VOB Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block type CBT (FIG. 16) of the cell playbackinformation blocks C_PBI #i containing the VOB control information foreach scene is declared as 01 b to indicate an “angle.”

At step #2374 the seamless playback flag SPF (FIG. 16) is set to 1 inthe cell playback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

At step #2376 the STC resetting flag STCDF is set to 1 in the cellplayback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

At step #2378 the interleaved allocation flag IAF (FIG. 16) is set to 1in the cell playback information blocks C_PBI #i containing the VOBcontrol information for each scene based on the multi-angle seamlessswitching flag VOB_FSV state, which is set to 1 to indicate interleavingis required.

At step #2380 the location of the navigation pack NV (relative sectornumber from the VOB beginning) is detected from the title editing unit(VOB below) obtained from the system encoder 900 in FIG. 25, thenavigation pack NV is detected based on the minimum interleaved unitpresentation time ILVU_MT information (a formatter parameter obtained instep #1854, FIG. 53), the location of the VOBU expressed as the numberof sectors from the VOB beginning, for example, is thus obtained, andthe title editing unit VOB is divided into interleave units using VOBUunits.

For example, if in this example the minimum interleaved unitpresentation time ILVU_MT is 2 sec and the presentation time of one VOBUis 0.5 sec., then the VOB is divided into interleave units of 4 VOBUeach. Note that this allocation operation is applied to the VOBconstituting each multi-scene data unit.

At step #2382 the interleave units of each VOB obtained from step #2380are arranged in the cell block mode CBM sequence (cell block beginning,middle, and end cells) written as the VOB control information for eachscene in step #2360 to form the interleaved blocks as shown in FIG. 37or 38. The interleaved blocks are then added to the VTS title VOBS(VTSTT_VOBS). Using the cell block mode CBM declarations above, forexample, the angle data MA1, MA2, and MA3 (FIG. 23) are arranged in thatsequence.

At step #2384 the relative sector number from the VOBU start is writtento the VOB end pack address VOBU_EA (FIG. 20) in the navigation pack NVof each VOBU based on the VOBU position information obtained in step#2360.

At step #2386 the first cell VOBU start address C_FVOBU_SA and the lastcell VOBU start address C_LVOBU_SA expressed as the number of sectorsfrom the beginning of the VTS title VOBS (VTSTT_VOBS) are written as theaddresses of the navigation packs NV of the first and last VOBU in eachcell based on the VTS title VOBS (VTSTT_VOBS) data obtained in step#2382.

At step #2388 the relative sector number from the VOBU start is writtento the VOB end pack address VOBU_EA (FIG. 20) in the navigation pack NVof each VOBU based on the interleave unit data obtained in step #2370.

The angle #i VOBU start address SML_AGL_C1_DSTA-SML_AGL_C9_DSTA of theseamless angle information SML_AGLI (FIG. 20) in the navigation pack NVof each VOBU is written at step #2390. This address is expressed as therelative sector number inside the data of the interleaved blocks formedin step #2382, and declares the address information (FIG. 50) of thenavigation pack NV contained in the VOBU of all angle scenes with astart time contiguous to the reproduction end time of the VOBU beingprocessed.

At step #2392 “7FFFFFFFh” is written to the angle #i VOBU start addressSML_AGL_Cl_DSTA_SML_AGL C9_DSTA of the seamless angle informationSML_AGLI (FIG. 20) in the navigation pack NV of the VOBU contained inthe interleaved unit if the interleave unit arranged in step #2382 isthe last interleave unit of each scene in the multi-scene period.

This routine thus formats the interleaved blocks for multi-angleseamless switching control in the multi-scene period, and formats thecell control information as the reproduction control information forthose multiple scenes.

The parental lock subroutine (step #2320, FIG. 56) executed when step#2318 in FIG. 56 returns NO, i.e., when it is determined that parentallock control is implemented and not multi-angle control, is describednext with reference to FIG. 59.

The parental lock subroutine described below writes the interleave unitarrangement of the multimedia bitstream, the content of the PGCinformation entries C_PBI #i (cell playback information) shown in FIG.16, and the navigation pack NV information shown in FIG. 20, to thegenerated DVD multimedia bitstream.

At step #2402 a value “00 b” is written to the cell block mode CBM (FIG.16) of the cell playback information blocks C_PBI #i containing the VOBcontrol information for each scene based on the multi-angle flag VOB_Fmstate, which is set to 0 to indicate that multi-angle control is notenabled in the multi-scene period.

At step #2404 the seamless playback flag SPF (FIG. 16) is set to 1 inthe cell playback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

At step #2406 the STC resetting flag STCDF is set to 1 in the cellplayback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

At step #2408 the interleaved allocation flag IAF (FIG. 16) is set to 1in the cell playback information blocks C_PBI #i containing the VOBcontrol information for each scene based on the multi-angle seamlessswitching flag VOB_FsV state, which is set to 1 to indicate interleavingis required.

At step #2410 the navigation pack NV position information (the relativesector number from the VOB start) is detected from the title editingunit (VOB) obtained from the system encoder 900 (FIG. 25). Thenavigation pack NV is then detected based on the number of interleavedVOB divisions ILV_DIV, a formatter parameter obtained in step #1874 inFIG. 55, to obtain the VOBU position information (number of sectors fromthe VOB start), and divide each VOB into the specified number ofinterleave units in VOBU units.

At step #2412 the interleave units obtained in step #2410 are theninterleaved. For example, the interleave units are arranged in ascendingVOB number sequence to create the interleaved blocks as shown in FIG. 37or 38, and the interleaved blocks are added to the VTS title VOBS(VTSTT_VOBS).

At step #2414 the relative sector number from the VOBU start is writtento the VOB end pack address VOBU_EA (FIG. 20) in the navigation pack NVof each VOBU based on the VOBU position information obtained in step#2186.

At step #2416 the first cell VOBU start address C_FVOBU_SA and the lastcell VOBU start address C_LVOBU_SA expressed as the number of sectorsfrom the beginning of the VTS title VOBS (VTSTT_VOBS) are written as theaddresses of the navigation packs NV of the first and last VOBU in eachcell based on the VTS title VOBS (VTSTT_VOBS) data obtained in step#2412.

At step #2418 the relative sector number to the last interleave unitpack is written to the ILVU end pack address ILVU_EA in the navigationpack NV of the VOBU forming the interleaved units based on theinterleaved unit data obtained from step #2412.

At step #2420, the relative sector number in the interleaved block dataformed in step #2412 is written to the next-ILVU start addressNT_ILVU_SA as the position information of the next ILVU in thenavigation packs NV of the VOBU contained in the interleaved unit ILVU.

At step #2422 the interleaved unit flag ILVU flag is set to 1 in thenavigation packs NV of the VOBU contained in the interleaved unit ILVU.

At step #2424, the Unit END flag of the navigation pack NV in the lastVOBU of the interleaved unit ILVU is set to 1.

At step #2426 “IFFFFFFFFh” is written to the next-ILVU start addressNT_ILVU_SA of the navigation pack NV of the VOBU in the last interleavedunit ILVU of each VOB.

The operation described above thus formats the interleaved blocks toenable parental lock control in the multi-scene periods, and formats thecontrol information in the cells, i.e., the cell playback controlinformation for the multi-scene periods.

The single scene subroutine executed as step #2314 in FIG. 56 when steps#2312 or #2316 return NO, i.e. , when the scene is determined to be asingle scene and not a multi-scene period, is described next using FIG.60.

The single scene subroutine described below writes the interleave unitarrangement of the multimedia bitstream, the content of the PGCinformation entries C_PBI #i (cell playback information) shown in FIG.16, and the navigation pack NV information shown in FIG. 20, to thegenerated DVD multimedia bitstream.

At step #2430 a value “00 b” indicating a “non-cell block”, i.e., thatthere is only one cell in the functional block, is written to the cellblock mode CBM (FIG. 16) of the cell playback information blocks C_PBI#i containing the VOB control information for each scene based on themulti-scene flag VOB_Fp state, which is set to 0 to indicate that thescene is a single scene and not part of a multi-scene period.

At step #2432 the interleaved allocation flag IAF (FIG. 16) is set to 0in the cell playback information blocks C_PBI #i containing the VOBcontrol information for each scene based on the multi-angle seamlessswitching flag VOB_FsV state, which is set to 0 to indicate interleavingis not required.

At step #2434 the navigation pack NV position information (the relativesector number from the VOB start) is detected from the title editingunit (VOB) obtained from the system encoder 900 (FIG. 25), placed in theVOBU unit, and added to the VTS title VOBS (VTSTT_VOBS), the video andother stream data of the multimedia bitstream.

At step #2436 the relative sector number from the VOBU start is writtento the VOB end pack address VOBU_EA (FIG. 20) in the navigation pack NVof each VOBU based on the VOBU position information obtained in step#2434.

At step #2438 the first cell VOBU start address C_FVOBU_SA and the lastcell VOBU start address C_LVOBU_SA expressed as the number of sectorsfrom the beginning of and the end of, respectively, the VTS title VOBS(VTSTT_VOBS) of the value written as the addresses of the navigationpacks NV of the first and last VOBU in cell based on the VTS title VOBS(VTSTT_VOBS) data obtained in step #2434.

At step #2440 the state determined as a result of step #300 or #600 inFIG. 51, i.e., whether preceding VOB seamless connection flag VOB_Fsb isset to 1 indicating a seamless connection to the preceding or followingscenes, is evaluated. If step #2440 returns YES, the procedure moves tostep #2442.

At step #2442 the seamless playback flag SPF (FIG. 16) is set to 1 inthe cell playback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1 to indicate a seamlessconnection.

At step #2444 the STC resetting flag STCDF is set to 1 in the cellplayback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 1.

If step #2.440 returns NO, i.e., there is not a seamless connection tothe preceding scene, the procedure moves to step #2446.

At step #2446 the seamless playback flag SPF (FIG. 16) is set to 0 inthe cell playback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 0 to indicate anon-seamless connection.

At step #2448 the STC resetting flag STCDF is set to 0 in the cellplayback information blocks C_PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB_Fsb state, which is set to 0.

The operation described above thus formats a multimedia bitstream for asingle scene period, and records the control information in the cells,i.e., the cell playback control information (C_PBI #i, FIG. 16), and theinformation in the navigation pack NV (FIG. 20), to the produced DVDmultimedia bitstream.

Decoder Flow Charts

A. Disk-to-stream buffer transfer flow

The decoding information table produced by the decoding systemcontroller 2300 based on the scenario selection data St51 is describedbelow referring to FIGS. 62 and 63. The decoding information tablecomprises the decoding system table shown in FIG. 62, and the decodingtable shown in FIG. 63.

As shown in FIG. 62, the decoding system table comprises a scenarioinformation register and a cell information register. The scenarioinformation register records the title number and other scenarioreproduction information selected by the user and extracted from thescenario selection data St51. The cell information register extracts andrecords the information required to reproduce the cells constituting theprogram chain PGC based on the user-defined scenario informationextracted into the scenario information register.

More specifically, the scenario information register contains pluralsub-registers, i.e., the angle number ANGLE_NO_reg, VTS numberVTS_NO_reg, PGC number VTS_PGCI_NO reg, audio ID AUDIO_ID_reg,sub-picture ID SP_ID_reg, and the system clock reference SCR bufferSCR_buffer.

The angle number ANGLE_No_reg stores which angle is reproduced whenthere are multiple angles in the reproduction program chain PGC.

The VTS number VTS_NO_reg records the number of the next VTS reproducedfrom among the plural VTS on the disk.

The PGC number VTS_PGCI_NO_reg records which of the plural programchains PGC present in the video title set VTS is to be reproduced forparental lock control or other applications.

The audio ID AUDIO_ID_reg records which of the plural audio streams inthe VTS are to be reproduced.

The sub-picture ID SP_ID_reg records which of the plural sub-picturestreams is to be reproduced when there are plural sub-picture streams inthe VTS.

The system clock reference SCR buffer SCR_buffer is the buffer fortemporarily storing the system clock reference SCR recorded to the packheader as shown in FIG. 19. As described using FIG. 26, this temporarilystored system clock reference SCR is output to the decoding systemcontroller 2300 as the bitstream control data St63.

The cell information register contains the following sub-registers: thecell block mode CBM_reg, cell block type CBT_reg, seamless reproductionflag SPF_reg, interleaved allocation flag IAF_reg, STC resetting flagSTCDF, seamless angle change flag SACF_reg, first cell VOBU startaddress C_FVOBU_SA_reg, and last cell VOBU start address C_LVOBU_SA_reg.

The cell block mode CBM_reg stores a value indicating whether pluralcells constitute one functional block. If there are not plural cells inone functional block, CBM_reg stores N_BLOCK. If plural cells constituteone functional block, the value F_CELL is stored as the CBM_reg value ofthe first cell in the block, L_CELL is stored as the CBM_reg value ofthe last cell in the block, and BLOCK is stored as the CBM_reg of valueall cells between the first and last cells in the block.

The cell block type CBT_reg stores a value defining the type of theblock indicated by the cell block mode CBM_reg. If the cell block is amulti-angle block, A_BLOCK is stored; if not, N_BLOCK is stored.

The seamless reproduction flag SPF_reg stores a value defining whetherthat cell is seamless connected with the cell or cell block reproducedtherebefore. If a seamless connection is specified, SML is stored; if aseamless connection is not specified, NSML is stored.

The interleaved allocation flag IAF_reg stores a value identifyingwhether the cell exists in a contiguous or interleaved block. If thecell is part of a an interleaved block, ILVB is stored; otherwise N_ILVBis stored.

The STC resetting flag STCDF defines whether the system time clock STCused for synchronization must be reset when the cell is reproduced; whenresetting the system time clock STC is necessary, STC_RESET is stored;if resetting is not necessary, STC_NRESET is stored.

The seamless angle change flag SACF_reg stores a value indicatingwhether a cell in a multi-angle period should be connected seamlessly atan angle change. If the angle change is seamless, the seamless anglechange flag SACF is set to SML; otherwise it is set to NSML.

The first cell VOBU start address C FVOBU_SA_reg stores the VOBU startaddress of the first cell in a block. The value of this address isexpressed as the distance from the logic sector of the first cell in theVTS title VOBS (VTSTT_VOBS) as measured by and expressed (stored) as thenumber of sectors.

The last cell VOBU start address C_LVOBU_SA_reg stores the VOBU startaddress of the last cell in the block. The value of this address is alsoexpressed as the distance from the logic sector of the first cell in theVTS title VOBS (VTSTT_VOBS) measured by and expressed (stored) as thenumber of sectors.

The decoding table shown in FIG. 63 is described below. As shown in FIG.63, the decoding table comprises the following registers: informationregisters for non-seamless multi-angle control, information registersfor seamless multi-angle control, a VOBU information register, andinformation registers for seamless reproduction.

The information registers for non-seamless multi-angle control comprisesub-registers NSML_AGL_C1_DSTA_reg-NSML_AGL_C9_DSTA_reg.

NSML_AGL_C1_DSTA_reg-NSML_AGL_C9_DSTA_reg record theNMSL_AGL_C1_DSTA-NMSL_AGL_C9_DSTA values in the PCI packet shown in FIG.20.

The information registers for seamless multi-angle control comprisesub-registers SML_AGL_C1_DSTA_reg-SML_AGL_C9_DSTA_reg.

SML_AGL_C1_DSTA_reg-SML_AGL_C9_DSTA_reg record theSML_AGL_C1_DSTA—SML_AGL_C9_DSTA values in the DSI packet shown in FIG.20.

The VOBU information register stores the end pack address VOBU_EA in theDSI packet shown in FIG. 20.

The information registers for seamless reproduction comprise thefollowing sub-registers: an interleaved unit flag ILVU_flag_reg, UnitEND flag UNIT_END_flag_reg, Interleaved Unit End Address ILVU_EA_reg,Next Interleaved Unit Start Address NT_ILVU_SA_reg, the presentationstart time of the first video frame in the VOB (Initial Video FramePresentation Start Time) VOB_V_SPTM_reg, the presentation end time ofthe last video frame in the VOB (Final Video Frame PresentationTermination Time) VOB_V_EPTM_reg, audio reproduction stopping time 1VOB_A_STP_PTMl_reg, audio reproduction stopping time 2VOB_A_STP_PTM2_reg, audio reproduction stopping period 1VOB_A_GAP_LEN1_reg, and audio reproduction stopping period 2VOB-A_GAP_LEN2_reg.

The interleaved unit flag ILVU_flag_reg stores the value indicatingwhether the video object unit VOBU is in an interleaved block, andstores ILVU if it is, and N_ILVU if not.

The Unit END flag UNIT_END_flag_reg stores the value indicating whetherthe video object unit VOBU is the last VOBU in the interleaved unitILVU. Because the interleaved unit ILVU is the data unit for continuousreading, the UNIT_END_flag_reg stores END if the VOBU currently beingread is the last VOBU in the interleaved unit ILVU, and otherwise storesN_END.

The Interleaved Unit End Address ILVU_EA_reg stores the address of thelast pack in the ILVU to which the VOBU belongs if the VOBU is in aninterleaved block. This address is expressed as the number of sectorsfrom the navigation pack NV of that VOBU.

The Next Interleaved Unit Start Address NT_ILVU_SA_reg stores the startaddress of the next interleaved unit ILVU if the VOBU is in aninterleaved block. This address is also expressed as the number ofsectors from the navigation pack NV of that VOBU.

The Initial Video Frame Presentation Start Time register VOB_V_SPTM_regstores the time at which presentation of the first video frame in theVOB starts.

The Final Video Frame Presentation Termination Time registerVOB_V_EPTM_reg stores the time at which presentation of the last videoframe in the VOB ends.

The audio reproduction stopping time 1 VOB_A_STP_PTM1_reg stores thetime at which the audio is to be paused to enable resynchronization, andthe audio reproduction stopping period 1 VOB_A_GAP_LEN1_reg stores thelength of this pause period.

The audio reproduction stopping time 2 VOB_A_STP_PTM2_reg and audioreproduction stopping period 2 VOB _A_GAP_LEN2_regstore the same values.

The operation of the DVD decoder DCD according to the present inventionas shown in FIG. 26 is described next below with reference to the flowchart in FIG. 69.

At step #310202 it is first determined whether a disk has been inserted.If it has, the procedure moves to step #310204.

At step #310204, the volume file structure VFS (FIG. 21) is read, andthe procedure moves to step #310206.

At step #310206, the video manager VMG (FIG. 21) is read and the videotitle set VTS to be reproduced is extracted. The procedure then moves tostep #310208.

At step #310208, the video title set menu address information VTSM_C_ADTis extracted from the VTS information VTSI, and the procedure moves tostep #310210.

At step #310210 the video title set menu VTSM_VOBS is read from the diskbased on the video title set menu address information VTSM_C_ADT, andthe title selection menu is presented.

The user is thus able to select the desired title from this menu in step#310212. If the titles include both contiguous titles with nouser-selectable content, and titles containing audio numbers,sub-picture numbers, or multi-angle scene content, the user must alsoenter the desired angle number. Once the user selection is completed,the procedure moves to step #310214.

At step #310214, the VTS_PGCI #i program chain (PGC) data blockcorresponding to the title number selected by the user is extracted fromthe VTSPGC information table VTS_PGCIT, and the procedure moves to step#310216.

Reproduction of the program chain PGC then begins at step #310216. Whenprogram chain PGC reproduction is finished, the decoding process ends.If a separate title is thereafter to be reproduced as determined bymonitoring key entry to the scenario selector, the title menu ispresented again (step #310210).

Program chain reproduction in step #310216 above is described in furtherdetail below referring to FIG. 64. The program chain PGC reproductionroutine consists of steps #31030, #31032, #31034, and #31035 as shown.

At step #31030 the decoding system table shown in FIG. 62 is defined.The angle number ANGLE_NO_reg, VTS number VTS_NO_reg, PGC numberVTS_PGCI_NO_reg, audio ID AUDIO_ID_reqg, and sub-picture ID SP_ID_regare set according to the selections made by the user using the scenarioselector 2100.

Once the PGC to be reproduced is determined, the corresponding cellinformation (PGC information entries C_PBI #j) is extracted and the cellinformation register is defined. The sub-registers therein that aredefined are the cell block mode CBM_reg, cell block type CBT_reg,seamless reproduction flag SPF_reg, interleaved allocation flag IAF_reg,STC resetting flag STCDF, seamless angle change flag SACF_reg, firstcell VOBU start address C_FVOBU_SA_reg, and last cell VOBU start addressC_LVOBU_SA_reg.

Once the decoding system table is defined, the process transferring datato the stream buffer (step -#31032) and the process decoding the data inthe stream buffer (step #31034) are activated in parallel.

The process transferring data to the stream buffer (step #31032) is theprocess of transferring data from the recording medium M to the streambuffer 2400. This is, therefore, the processing of reading the requireddata from the recording medium M and inputting the data to the streambuffer 2400 according to the user-selected title information and theplayback control information (navigation packs NV) written in thestream.

The routine shown as step #31034 is the process for decoding the datastored to the stream buffer 2400 (FIG. 26), and outputting the decodeddata to the video data output terminal 3600 and audio data outputterminal 3700. Thus, is the process for decoding and reproducing thedata stored to the stream buffer 2400.

Note that step #31032 and step #31034 are executed in parallel.

The processing unit of step #31032 is the cell, and as processing onecell is completed, it is determined in step #31035 whether the completeprogram chain PGC has been processed. If processing the complete programchain PGC is not completed, the decoding system table is defined for thenext cell in step #31030. This loop from step #31030 through step #31035is repeated until the entire program chain PGC is processed.

The stream buffer data transfer process of step #31032 is described infurther detail below referring to FIG. 70. The stream buffer datatransfer process (step #31032) comprises steps #31040, #31042, #31044,#31046, and #31048 shown in the figure.

At step #31040 it is determined whether the cell is a multi-angle cell.If not, the procedure moves to step #30144.

At step #31044 the non-multi-angle cell decoding process is executed.

However, if step #30140 returns YES because the cell is a multi-anglecell, the procedure moves to step #30142 where the seamless angle changeflag SACF is evaluated to determine whether seamless angle reproductionis specified.

If seamless angle reproduction is specified, the seamless multi-angledecoding process is executed in step #30146. If seamless anglereproduction is not specified, the non-seamless multi-angle decodingprocess is executed in step #30148.

The non-multi-angle cell decoding process (step #31044, FIG. 70) isdescribed further below with reference to FIG. 71. Note that thenon-multi-angle cell decoding process (step #31044) comprises the steps#31050, #31052, and #31054.

The first step #31050 evaluates the interleaved allocation flag IAF_regto determine whether the cell is in an interleaved block. If it is, thenon-multi-angle interleaved block process is executed in step #31052.

The non-multi-angle interleaved block process (step #31052) processesscene branching and connection where seamless connections are specifiedin, for example, a multi-scene period.

However, if the cell is not in an interleaved block, the non-multi-anglecontiguous block process is executed in step #31054. Note that the step#31054 process is the process executed when there is no scene branchingor connection.

The non-multi-angle interleaved block process (step #31052, FIG. 71) isdescribed further below with reference to FIG. 72.

At step #31060 the reading head 2006 is jumped to the first cell VOBUstart address C_FVOBU_SA read from the C_FVOBU_SA_reg register.

More specifically, the address data C_FVOBU_SA_reg stored in thedecoding system controller 2300 (FIG. 26) is input as bitstreamreproduction control signal St53 to the reproduction controller 2002.The reproduction controller 2002 thus controls the recording media driveunit 2004 and signal processor 2008 to move the reading head 2006 to thespecified address, data is read, error correction code ECC and othersignal processing is accomplished by the signal processor 2008, and thecell start VOBU data is output as the reproduced bitstream St61 to thestream buffer 2400. The procedure then moves to step #31062.

At step #31062 the DSI packet data in the navigation pack NV (FIG. 20)is extracted in the stream buffer 2400, the decoding table is defined,and the procedure moves to step #31064. The registers set in thedecoding table are the ILVU_EA_reg, NT_ILVU_SA_reg, VOB_V_SPTM_reg,VOB_V_EPTM_reg, VOB_A_STP_PTM1_reg, VOB_A_STP_PTM2_reg,VOB_A_GAP_LEN1_reg, and VOB_A_GAP_LEN2_reg.

At step #31064 the data from the first cell VOBU start addressC_FVOBU_SA_reg to the ILVU end pack address ILVU_EA_reg, i.e., the datafor one interleaved unit ILVU, is transferred to the stream buffer 2400.The procedure then moves to step #31066.

More specifically, the address data ILVU_EA_reg stored in the decodingsystem controller 2300 (FIG. 26) is supplied to the reproductioncontroller 2002. The reproduction controller 2002 thus controls therecording media drive unit 2004 and signal processor 2008 to read thedata to the ILVU_EA_reg address, and after error correction code ECC andother signal processing is accomplished by the signal processor 2008,the data for the first ILVU in the cell is output as the reproducedbitstream St61 to the stream buffer 2400. It is thus possible to outputthe data for one contiguous interleaved unit ILVU on the recordingmedium M to the stream buffer 2400.

At step #31066 it is determined whether all interleaved units in theinterleaved block have been read and transferred. If the interleavedunit ILVU processed is the last ILVU in the interleaved block,“0×7FFFFFFF” indicating termination is set to the next-ILVU startaddress NT_ILVU_SA_reg as the next read address. If all interleavedunits in the interleaved block have thus been processed, the proceduremoves to step #31068.

At step #31068 the reading head 2006 is again jumped to the addressNT_ILVU_SA_reg of the next interleave unit to be reproduced, and theprocedure loops back to step #31062. Note that this jump is alsoaccomplished as described above, and the loop from step #31062 to step#31068 is repeated.

However, if step #31066 returns YES, i.e., all interleaved unit ILVU inthe interleaved block have been transferred, step #31052 terminates.

The non-multi-angle interleaved block process (step #31052) thustransfers the data of one cell to the stream buffer 2400.

The non-multi-angle contiguous block process is executed in step #31054,FIG. 71, is described further below with reference to FIG. 73.

At step #31070 the reading head 2006 is jumped to the first cell VOBUstart address C_FVOBU_SA read from the C_FVOBU_SA_reg register. Thisjump is also accomplished as described above, and the loop from step#31072 to step #31076 is initiated.

At step #31072 the DSI packet data in the navigation pack NV (FIG. 20)is extracted in the stream buffer 2400, the decoding table is defined,and the procedure moves to step #31074. The registers set in thedecoding table are the VOBU_EA_reg, VOB_V_SPTM_reg, VOB_V_EPTM_reg,VOB_A_STP_PTM1_reg, VOB_A_STP_PTM2_reg, VOB_A_GAP_LEN1_reg, andVOB_A_GAP_LEN2_reg.

At step #31074 the data from the first cell VOBU start addressC_FVOBU_SA_reg to the end pack address VOBU_EA_reg, i.e., the data forone video object unit VOBU, is transferred to the stream buffer 2400.The procedure then moves to step #31076. The data for one video objectunit VOBU contiguously arrayed to the recording medium M can thus betransferred to the stream buffer 2400.

At step #31076 it is determined whether all cell data has beentransferred. If all VOBU in the cell has not been transferred, the datafor the next VOBU is read continuously, and the process loops back tostep #31070.

However, if all VOBU data in the cell has been transferred as determinedby the C_LVOBU_SA_reg value in step #31076, the non-multi-anglecontiguous block process (step #31054) terminates. This process thustransfers the data of one cell to the stream buffer 2400.

Another method of accomplishing the non-multi-angle cell decodingprocess (step #31044, FIG. 70) is described below with reference to FIG.72.

At step #31080 the reading head 2006 is jumped to the first cell VOBUstart address C_FVOBU_SA_reg, and the first VOBU data in the cell istransferred to the stream buffer 2400. The procedure then moves to step#31081.

At step #31081 the DSI packet data in the navigation pack NV (FIG. 20)is extracted in the stream buffer 2400, the decoding table is defined,and the procedure moves to step #31082. The registers set in thedecoding table are the SCR_buffer, VOBU_EA_reg, ILVU_flag_reg,UNIT_END_flag_reg, ILVU_EA_reg, NT_ILVU_SA_reg, VOB_V_SPTM_reg,VOB_V_EPTM_reg, VOB_A_STP_PTM1_reg, VOB_A_STP_PTM2_reg,VOB_A_GAP_LEN1_reg, and VOB_A GAP_LEN2_reg.

At step #31082 the data from the first cell VOBU start addressC_FVOBU_SA_reg to the end pack address VOBU_EA_reg, i.e., the data forone video object unit VOBU, is transferred to the stream buffer 2400.The procedure then moves to step #31083.

At step #31083 is determined whether all cell VOBU data has beentransferred. If it has, the process (step #31044) terminates. If it hasnot, the procedure moves to step #31084.

At step #31084 it is determined whether the VOBU is the last VOBU in theinterleaved unit. If not, the process loops back to step #31081. If so,the procedure advances to step #31085. It is thus possible to transferone cell of data in VOBU units to the stream buffer 2400.

The loop from step #31081 to step #31084 repeats as described above.

At step #31085 it is determined whether the interleaved unit ILVU is thelast in the interleaved block. If so, step #31044 terminates. If not,the procedure advances to step #31086.

At step #31086 the reading head 2006 is jumped to the addressNT_ILVU_SA_reg of the next interleave unit, and the procedure loops backto step #31081. It is thus possible to transfer the data for one cell tothe stream buffer 2400.

The seamless multi-angle decoding process executed in step #30146, FIG.70, is described below referring to FIG. 75.

At step #31090 the reading head 2006 is jumped to the first cell VOBUstart address C_FVOBU_SA read from the C_FVOBU_SA_reg register, and thefirst VOBU data in the cell is transferred to the stream buffer 2400.The procedure then moves to step #31091. This jump is also accomplishedas described above, and the loop from step #31091 to step #31095 isinitiated.

At step #31091 the DSI packet data in the navigation pack NV (FIG. 20)is extracted in the stream buffer 2400, the decoding table is defined,and the procedure moves to step #31092. The registers set in thedecoding table are the ILVU_EA_reg,SML_AGL_C1_DSTA_reg-SML_AGL_C9_DSTA_reg, VOB_V_SPTM_reg, VOB_V_EPTM_reg.VOB_A_STP_PTM1_reg, VOB_A_STP_PTM2_reg, VOB_A_GAP_LEN1_reg, andVOB_A_GAP_LEN2_reg.

At step #31092 the data from the first cell VOBU start addressC_FVOBU_SA_reg to the ILVU end pack address ILVU_EA_reg, i.e., the datafor one ILVU, is transferred to the stream buffer 2400. The procedurethen moves to step #31093. It is thus possible to output the data forone contiguous interleaved unit ILVU on the recording medium M to thestream buffer 2400.

At step #31093 the ANGLE_NO_reg is updated, and the procedure moves tostep #31094. This update operation resets the ANGLE_NO_reg to the anglenumber of the angle selected by the user when the user changes the angleusing the scenario selector 2100 (FIG. 26).

At step #31094 it is determined whether the angle cell data has all beentransferred. If all ILVU in the cell have not been transferred, theprocedure moves to step #31095. If all ILVU in the cell have beentransferred, the process terminates.

At step #31095 the reading head 2006 is jumped to the next angle(SML_AGL_C#n_reg), and the process loops back to step #31091. Note thatSML_AGL_C#n_reg is the address of the angle to which the ANGLE_NO_regwas updated in step #31093.

It is thus possible to transfer the data for the angle selected by theuser to the stream buffer 2400 in ILVU units.

The non-seamless multi-angle decoding process is executed in step#30148, FIG. 70, is described below referring to FIG. 65.

At step #31100 the reading head 2006 is jumped to the first cell VOBUstart address C_FVOBU_SA read from the C_FVOBU_SA_reg register, and thefirst VOBU data in the cell is transferred to the stream buffer 2400.The procedure then moves to step #31101. This jump is also accomplishedas described above, and the loop from step #31101 to step #31106 isinitiated.

At step #31101 the DSI packet data in the navigation pack NV (FIG. 20)is extracted in the stream buffer 2400, the decoding table is defined,and the procedure moves to step #31102. The registers set in thedecoding table are the VOBU_EA_reg, NSML_AGL_C1_DSTA_reg,NSML_AGL_C9_DSTA_reg, VOB_V_SPTM_reg, VOB_V_EPTM_reg,VOB_A_STP_PTM1_reg, VOB_A_STP_PTM2_reg, VOB_A_GAP_LEN1_reg, and VOB_AGAP_LEN2_reg.

At step #31102 the data from the first cell VOBU start addressC_FVOBU_SA_reg to the end pack address VOBU_EA_reg, i.e., the data forone VOBU, is transferred to the stream buffer 2400. The procedure thenmoves to step #31103. It is thus possible to output the data for onecontiguous video object unit VOBU on the recording medium M to thestream buffer 2400.

At step #31103 the ANGLE_NO_reg is updated, and the procedure moves tostep #31104. This update operation resets the ANGLE_NO_reg to the anglenumber of the angle selected by the user when the user changes the angleusing the scenario selector 2100 (FIG. 26).

At step #31104 it is determined whether the angle cell data has all beentransferred. If all VOBU in the cell have not been transferred, theprocedure moves to step #31105. If all VOBU in the cell have beentransferred, the process terminates.

At step #31105 the reading head 2006 is jumped to the next angle(NSML_AGL_C#n_reg), and the process advances to step #31106. Note thatNSML_AGL_C#n_reg is the address of the angle to which the ANGLE_NO_regwas updated in step #31103.

It is thus possible to transfer the data for the angle selected by theuser to the stream buffer 2400 in VOBU units.

Step #31106 is an effective step for high speed angle switching, andsimply clears the stream buffer 2400. By thus clearing the stream buffer2400 the data for the newly selected angle can be reproduced withoutreproducing the angle data that is still not decoded. In other words,clearing the stream buffer 2400 enables faster response to useroperations.

It is very important that DVD decoder according to the present inventioncan promptly moves to the next data reading process and effectivelyperforms the data reading once after the detection of the end of datasuch as interleave unit ILVU and video object unit VOBU for the sake ofseamless reproduction which is one of main targets of the presentinvention.

With reference to FIG. 66, a construction of the stream buffer 2400which can performs the end detection of interleave unit ILVU isdescribed briefly. The stream buffer 2400 comprises a VOB buffer 2402, asystem buffer 2404, a navigation pack extractor 2406, and a data counter2408. The system buffer 2404 temporarily stores the title control dataVTSI(FIG. 16) included in signal St61, and outputs a control informationSt2450 (St63) such as VTS_PGC.

The VOB buffer 2402 temporarily stores the title VOB data VTSTT_VOB(FIG. 1002), and the stream St67 to the system decoder 2500.

The NV (navigation pack) extractor 2406 receives the VOB data at thesame time with the VOB buffer 2402, and extracts the navigation pack NVtherefrom. The NV extractor 2406 furthermore extracts the VOBU finalpack address COBU_EA or ILVU final pack address ILVU_EA which are theDSI generation information DSI_GI shown in FIG. 19 to produce a packaddress information St2452 (St63).

The data counter 2408 receives the VOB data at the same time with theVOB buffer 2402, and counts each of pack data shown in FIG. 19 byte bybye. Then, the data counter 2408 produces a pack input terminatingsignal St2454 (St63) at the time when the inputting of pack data iscompleted.

Due to its construction shown in FIG. 66, the stream buffer 2400performs the VOBU data transfer as examples at step #31064 of FIG. 72,as follows. The stream buffer 2400 outputs the VOBU data for the NVextractor 2406 and data counter 2408 at the same time when the VOBUbuffer 2400 receives the VOBI data on the top of interleave unit ILVU.As a result, the NV extractor 2406 can extracts the data of ILVU_EA andNT_ILVU_SA at the same time with the inputting of navigation pack dataNV, and outputs thereof as signal St2452 (St63) to the decode systemcontroller 2300 (FIG. 26).

The decode system controller 2300 stores the signal St2452 into theILVU_EA_reg and NT_ILVU_SA_reg, and then start to counts the number ofpacks based on the pack terminating signal 2452 from the data counter2408. Based on the fore mentioned the counted value of packs andILVU_EA_reg, the decode system controller 2300 detects the instance whenthe inputting of final pack data of ILVU is completed, or the inputtingfinal byte data of the final pack of the ILVU is completed. Then, thecontroller 2300 further give a command for the bitstream reproducer 2000to move to the position having a sector address indicated byNT_ILVU_SA_reg. The bitstream producer 2000 moves to the sector addressindicated NT_ILVU_SA_reg, and starts to read the data. Thus, thedetection of final end of ILVU and reading process for the next ILVU canbe performed effectively.

In the above, an example where the multimedia data MBS is reproduced bythe bitstream reproducer 2000 without a buffering process, and isinputted to the stream buffer 2499. However, in the case that the signalprocessor 2008 of the bitstream reproducer 2000 is incorporated with abuffer for error correction process, for example, the controller 2300gives a moving command to reproducer 2000 so that the reproducer 2000moves to the reading position indicated by NT_ILVU_SA_reg aftercompletion of the final pack data of fore mentioned ILVU and clearingthe internal buffer of the reproducer 2000. Thus, the effectivereproduction of ILVU data even when the bitstream reproducer 2000includes a buffer for error correction code (ECC) process.

Furthermore, when the bitstream producer 2000 has a buffer for ECCprocess, the data can be transferred effectively by providing any meanshaving a function equivalent to that of data counter 2408 (FIG. 66). Inother words, the bitstream reproducer 2000 generates the pack inputcompletion signal St62; the decode system controller 2300 gives acommand based on the signal St62 the bitstream reproducer 200 to move tothe reading position having sector address designated by NT_ILVU_SA_reg.As apparent from the above, the data can be transferred effectively evenwhen the bitstream reproducer 2000 has a function to buffer the datareproduced from the recording media M.

It is to be noted that the apparatus and method substantially the sameas those described in the above with respect to the interleave unit ILVUcan be used for the detection VOBU end. In other words, by replacing theextraction of ILVU_EA and NT_ILVU_Sa, and the storing of ILVU_EA_reg andNT_ILVU_SA_reg with the extraction of VOBU_EA and storing VOBU_EA_reg,the apparatus and method according to the present invention, describedabove, can be used for the detection of unatend. This is effective forthe VOBU data transferring operations shown at steps #31074, #31082,#31092, and #31102.

Thus, the reading of data such as ILVU and VOBU can be performedeffectively. Decoding process in the stream buffer

The process for decoding data in the stream buffer 2400 shown as step#31034 in FIG. 64 is described below referring to FIG. 67. This process(step #31034) comprises steps #31110, #31112, #31114, and #31116.

At step #31110 data is transferred in-pack units from the stream buffer2400 to the system decoder 2500 (FIG. 26). The procedure then moves tostep #31112.

At step #31112 the pack data is from the stream buffer 2400 to each ofthe buffers, i.e., the video buffer 2600, sub-picture buffer 2700, andaudio buffer 2800.

At step #31112 the Ids of the user-selected audio and sub-picture data,i.e., the audio ID AUDIO_ID_reg and the sub-picture ID SP_ID_reg storedto the scenario information register shown in FIG. 62, are compared withthe stream ID and sub-stream ID read from the packet header (FIG. 19),and the matching packets are output to the respective buffers. Theprocedure then moves to step #31114.

The decode timing of the respective decoders (video, sub-picture, andaudio decoders) is controlled in step #31114, i.e., the decodingoperations of the decoders are synchronized, and the procedure moves tostep #31116.

Note that the decoder synchronization process of step #31114 isdescribed below with reference to FIG. 68.

The respective elementary strings are then decoded at step #31116. Thevideo decoder 3801 thus reads and decodes the data from the videobuffer, the sub-picture decoder 3100 reads and decodes the data from thesub-picture buffer, and the audio decoder 3200 reads and decodes thedata from the audio buffer.

This stream buffer data decoding process then terminates when thesedecoding processes are completed.

The decoder synchronization process of step #31114, FIG. 67, isdescribed below with reference to FIG. 68. This processes comprisessteps #31120, #31122, and #31124.

At step #31120 it is determined whether a seamless connection isspecified between the current cell and the preceding cell. If a seamlessconnection, the procedure moves to step #31122, if not, the proceduremoves to step #31124.

A process synchronizing operation for producing seamless connections isexecuted in step #31122, and a process synchronizing operation fornon-seamless connections is executed in step #31124.

By means of the present invention thus described it is possible to readand supply to a decoder the source data for plural video objects withoutinterruptions in the data during reproduction. When reproducing pluralvideo objects of the same length, it is also possible to seamlesslyreproduce the video objects without intermitting the data or thepresentation time even from a midpoint in a video object.

It is also possible to supply the data of plural video objects to thedecoder without intermitting the data during presentation. Plural videoobjects can also be reproduced by reading only the necessary informationand seamlessly switching the presented video object without intermittingthe data during presentation.

Switching between plural video objects can also be accomplished at highspeed even while presentation is in progress. Furthermore, it ispossible to dynamically switch to another system stream according to auser selection even while in the middle of video object presentationwhen reproducing data from an optical disk, and these dynamic systemstream changes can be executed seamlessly.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

What is claimed is:
 1. A bit stream generating method for generating abit stream stored to a disc reproduced by a disc reproducing apparatus,where said disc reproducing apparatus comprises a track buffer fortemporarily storing data read from the disc to the track buffer at aread rate Vr before transferring said data to a decoder at a supply rateVo, where said read rate Vr is greater than said supply rate Vo, andsaid bit stream comprises a plurality of video objects (VOB) of whichone is alternatively reproduced from among m video objects (VOB); saidbit stream generating method comprises steps for: selecting m videoobjects (VOB), obtaining a time t2 at which reading a bit stream fromthe disc will be interrupted when an optical head of the discreproducing apparatus jumps between an interleave unit (ILVU_(ij)) andan interleave unit (ILVU_(i(j+1))) when each of selected m video objects(VOB) is segmented into v interleave units (ILVU_(ij)) interleaved in asequence ILVU₁₁ . . . ILVU₂₁ . . . ILVU_((m−1)1) . . . ILVU_(m1) . . .ILVU₁₂ . . . ILVU₂₂ . . . ILVU_((m−1)2) . . . ILVU_(m2) . . .ILVU_(1(v−1)). . . ILVU_(2(v−1)). . . ILVU_((m−1)(v−1)). . .ILVU_(m(v−1)). . . ILVU_(1v). . . ILVU_(2v). . . ILVU_((m−1)1) . . .ILVU_(mv). . . where i is a sequential value indicative of a videoobject (VOB) and ranges from 1 to m, and j is a sequential valueindicative of an interleave unit (ILVU) and ranges from 1 to v,obtaining a data quantity d1 stored to the track buffer at adifferential rate Vr−Vo during a time t1, said time t1 being a periodduring which a bit stream constituting said interleave unit (ILVU_(ij))is read from disc, segmenting m video objects into interleave units(ILVU_(ij)) whereby said data quantity d1 stored to the track bufferexceeds a data quantity d2 transferred at supply rate Vo from the trackbuffer to the decoder during said time t2, and generating a bit streamin which segmented m video objects (VOB) are interleaved in the sequencedescribed above.
 2. A bit stream generating method according to claim 1,wherein a video object (VOB) contains compressed image data, and thestep for selecting a video object (VOB) selects mn video objects (VOB)having the same presentation time for the uncompressed image datacontained therein.
 3. A bit stream generating method according to claim1, wherein said video object (VOB) contains image data compressedaccording to a MPEG standard, and a smallest control unit (VOBU) whichis a sub region of said video object (VOB) constituting an interleaveunit (ILVU) is bounded by a GOP unit, which is an image data compressionunit.
 4. An optical disc (M) for storing a bit stream reproduced by adisc reproducing apparatus, said bit stream comprising a plurality ofvideo objects (VOB) of which one is alternatively reproduced from amongm video objects (VOB), wherein said disc comprises a video objectstorage area and a management information storage area, said managementinformation storage area stores presentation sequence informationindicative of the video object (VOB) presentation sequence, and groupinformation indicative of what video object (VOB) and what otheralternatively reproducible video object (VOB) are associated with thesame group, said video object (VOB) storage area stores one or morevideo objects (VOB) where each of m (where m is an integer value of twoor more) video objects (VOB) associated with a same group is segmentedinto v interleave units (ILVU_(ij)), where i is a sequential valueindicative of a video object (VOB) and ranges from 1 to m, and j is asequential value indicative of an interleave unit (ILVU) and ranges from1 to v, and said interleave units (ILVU_(ij)) are arranged in a sequenceILVU₁₁. . . ILVU₂₁. . . ILVU₁₂ . . . ILVU₂₂ . . . ILVU_((m−1)2) . . .ILVU_(m2) . . . ILVU_(1(v−1)). . . ILVU_(2(v−1)). . . ILVU_((m−1)(v−1)).. . ILVU_(m(v−1)). . . ILVU_(1v). . . ILVU_(2v). . . ILVU_((m−1)1) . . .ILVU_(mv). said interleave units (ILVU_(ij)) are segmented from m videoobjects (VOB) in such a manner that a disc reproducing apparatus issupplied with data sufficient to sustain presentation for a time t3,where time t3 is a sum of time t1 and a time t2, time t1 being a timerequired to read a bit stream constituting said interleave units(ILVU_(ij)) from a disc, and time t2 being a time required for the discreproducing apparatus to switch bit stream reproduction from interleaveunit (ILVU_(ij)) to interleave unit (ILVU_(ij)) to interleave unitILVU_(i(i,j,))), and said interleave unit comprises one or more subregions (VOBU) to which video data and management information (NV) arestored, and said management information (NV) comprises end addressinformation (ILVU_EA) indicative of an end address of the associatedinterleave unit (ILVU), and linking information (NT_ILVU_SA) indicativeof a position on the disc (M) of a next interleave unit (ILVU) to bereproduced.
 5. A disc (M) for storing a bit stream reproduced by a discreproducing apparatus according to claim 4, where said disc reproducingapparatus comprises a track buffer for temporarily storing data readfrom the disc to the track buffer at a read rate Vr before transferringsaid data to a decoder at a supply rate Vo, where said read rate Vr isgreater than said supply rate Vo, and said bit stream comprises aplurality of video objects (VOB) of which one is alternativelyreproduced from among m video objects (VOB); wherein said interleaveunits (ILVUij) are segmented from m video objects (VOB) in such a waythat a data quantity d1 stored to the track buffer at a differentialrate Vr−Vo during a time t1 exceeds a data quantity d2 transferred atsupply rate Vo from the track buffer to the decoder during a time t2,said time t1 being a period during which a bit stream constituting saidinterleave unit (ILVU_(ij)) is read from disc, and said time t2 being atime at which reading a bit stream from the disc will be interruptedwhen a head of the disc reproducing apparatus jumps between aninterleave unit (ILVU_(ij)) and an interleave unit (ILVU_(i(j+1)).
 6. Adisc (M) according to claim 4, wherein the end position information ofan interleave unit comprises in the management information of a subregion, end address information (VOBU_EA) of the associated sub region,and a flag (UNIT_END_flag) indicating whether the interleave unitterminates in the associated sub region.
 7. A disc (M) according toclaim 4, wherein m video objects (VOB) associated with a same groupcontain compressed image data having the same presentation time whenuncompressed, and sub region (VOBU) management information (NV) containsend address information (VOBU_EA) indicative of an end address of theassociated sub region on disc, a flag (UNIT_END_flag) indicative of anend of an interleave unit, linking information (NT_ILVU_SA) indicativeof a position on the disc (M) of a next interleave unit (ILVU) to bereproduced, and angle-specific linking information (SML_AGL_C#1-9_DSTA)indicative of a position on the disc (M) of a next interleave unit(ILVU) to be reproduced for each video object (VOB) associated with asingle GOP during alternative presentation.
 8. A disc (M) according toclaim 4, wherein sub region (VOBU) image data is image data compressedusing an MPEG method, and said sub region (VOBU) is bounded by a GOPunit, which is an image data compression unit.
 9. A disc reproducingapparatus (DCD) comprising a means for reading presentation sequenceinformation, group information, and a video object (VOB) from a disc (M)according to claim 4, a retrieving means for retrieving managementinformation (NV) from a read video object (VOB), buffer for storing themanagement information (NV), a presentation control means forcontrolling video object presentation according to a presentationsequence indicated by the presentation sequence information, an anglepresentation detection means for detecting whether a read video objectis an alternatively presentable video object based on the groupinformation, an angle selection means for selecting one video objectwhen a read video object is an alternatively presentable video object,an interleave unit end detection means for referencing end addressinformation (ILVU_EA) for an interleave unit contained in the managementinformation of a sub region being presented, and detecting whetherpresentation of an interleave unit has reached the end, and an anglepresentation control means for presenting a selected video object when aread video object is an alternatively presentable video object, and whenpresentation has reached an end of an interleave unit, resumingpresentation of a video object from an interleave unit indicated bylinking information (NT_ILVU_SA) in the stored management information(NV).
 10. A disc reproducing apparatus (DCD) according to claim 9,further comprising a means for reading presentation sequenceinformation, group information, and a video object (VOB) from a disc(M), said disc (M) comprising a video object storage area and amanagement information storage area, said management information storagearea stores presentation sequence information indicative of the videoobject (VOB) presentation sequence, and group information indicative ofwhat video object (VOB) and what other alternatively reproducible videoobject (VOB) are associated with the same group, said video object (VOB)storage area stores one or more video objects (VOB) where each of m(where m is an integer value of two or more) video objects (VOB)associated with a same group is segmented into v interleave units(ILVU_(ij)), where i is a sequential value indicative of a video object(VOB) and ranges from 1 to m, and j is a sequential value indicative ofan interleave unit (ILVU) and ranges from 1 to v, and said interleaveunits (ILVU_(ij)) are arranged in a sequence ILVU₁₁. . . ILVU₂₁ . . .ILVU_((m−1)1). . . ILVU_(m1). . . ILVU₁₂ . . . ILVU₂₂ . . .ILVU_((m−1)2) . . . ILVU_(m2) . . . ILVU_(1(v−1)). . . ILVU_(2(v−1)). .. ILVU_((m−1)(v−1)). . . ILVU_(m(v−1)). . . ILVU_(1v). . . ILVU_(2v). .. ILVU_((m−1)1) . . . ILVU_(mv), said interleave units (ILVU_(ij)) aresegmented from m video objects (VOB) in such a manner that a discreproducing apparatus is supplied with data sufficient to sustainpresentation for a time t3, where time t3 is a sum of time t1 and a timet2, time t1 being a time required to read a bit stream constituting saidinterleave units (ILVU_(ij)) from a disc, and time t2 being a timerequired for the disc reproducing apparatus to switch bit streamreproduction from interleave unit (ILVUij) to interleave unit(ILVU_(ij)) to interleave unit ILVU_(i(j+1)), and said interleave unitcomprises one or more sub regions (VOBU) to which video data andmanagement information (NV) are stored, and said management information(NV) comprises end address information (ILVU_EA) indicative of an endaddress of the associated interleave unit (ILVU), and linkinginformation (NT_ILVU_SA) indicative of a position on the disc (M) of anext interleave unit (ILVU) to be reproduced, wherein the end positioninformation of an interleave unit comprises in the managementinformation of a sub region, end address information (VOBU_EA) of theassociated sub region, and a flag (UNIT_END_flag) indicating whether theinterleave unit terminates in the associated sub region; wherein theinterleave unit end detection means detects whether presentation of avideo object (VOB) has reached the end of an interleave unit based onend address information (VOBU-EA) for a sub region on disc, and a flag(UNIT_END_flag) indicative of an end of an interleave unit.
 11. A discreproducing apparatus (DCD) according to claim 9, further comprising anangle change acceptance means and an angle change control means, whereinsaid reading means reads presentation sequence information, groupinformation, and a video object (VOB) from a disc (M), said disc (M)comprising a video object storage area and a management informationstorage area, said management information storage area storespresentation sequence information indicative of the video object (VOB)presentation sequence, and group information indicative of what videoobject (VOB) and what other alternatively reproducible video object(VOB) are associated with the same group, said video object (VOB)storage area stores one or more video objects (VOB) where each of m(where m is an integer value of two or more) video objects (VOB)associated with a same group is segmented into v interleave units(ILVU_(ij)), where i is a sequential value indicative of a video object(VOB) and ranges from 1 to m, and j is a sequential value indicative ofan interleave unit (ILVU) and ranges from 1 to v, and said interleaveunits (ILVU_(ij)) are arranged in a sequence ILVU₁₁ . . . ILVU₂₁ . . .ILVU_((m−1)1) . . . ILVU_(m1) . . . ILVU₁₂ . . . ILVU₂₂ . . .ILVU_((m−1)2) . . . ILVU_(m2) . . . ILVU_(1(v−1)). . . ILVU_(2(v−1)). .. ILVU_((m−1)(v−1)). . . ILVU_(m(v−1)). . . ILVU_(1v). . . ILVU_(2v). .. ILVU_((m−1)v). . . ILVU_(mv), said interleave units (ILVUij) aresegmented from m video objects (VOB) in such a manner that a discreproducing apparatus is supplied with data sufficient to sustainpresentation for a time t3, where time t3 is a sum of time t1 and a timet2, time t1 being a time required to read a bit stream constituting saidinterleave units (ILVUij) from a disc, and time t2 being a time requiredfor the disc reproducing apparatus to switch bit stream reproductionfrom interleave unit (ILVU_(ij)) to interleave unit (ILVU) to interleaveunit ILVU_(i(j+1)), and said interleave unit comprises one or more subregions (VOBU) to which video data and management information (NV) arestored, and said management information (NV) comprises end addressinformation (ILVU_EA) indicative of an end address of the associatedinterleave unit (ILVU), and linking information (NT_ILVU_SA) indicativeof a position on the disc (M) of a next interleave unit (ILVU) to bereproduced, said angle change acceptance means accepts an instructionchanging a video object (VOB) to be alternatively presented, anddetermines a presentation start position for the alternatively selectedvideo object according to the angle-specific linking information(SML_AGL_C#1-9_DSTA) in the management information (NV), and said anglechange control means starts presentation of the specified alternativelypresentable video object from a determined presentation startingposition when an angle change instruction is received.
 12. Areproduction method for a disc according to claim 4, comprising stepsof: selecting a video object to be presented, reading the selected videoobject, retrieving and storing management information (NV) from the readvideo object, presenting the read video object, detecting whetherpresentation of a video object has continued to an end of an interleaveunit based on interleave unit end address information (ILVU_EA)contained in the management information (NV), and resuming video objectpresentation from a position indicated by a linking information(NT_ILVU_SA) in the stored management information when video objectpresentation has been completed to an interleave unit end.
 13. Areproduction method for a disc according to claim 6, comprising stepsof: selecting a video object to be presented, reading the selected videoobject, retrieving and storing management information (NV) from the readvideo object, presenting the read video object, detecting whetherpresentation of a video object has continued to an end of an interleaveunit based on end address information (ILVU_EA) indicative of an endaddress of the associated sub region on disc, and a flag (UNIT_END_flag)indicative of an end of an interleave unit, contained in the managementinformation (NV), and resuming video object presentation from a positionindicated by a linking information (NT_ILVU_SA) in the held managementinformation when video object presentation has been completed to aninterleave unit end.
 14. A reproduction method for a disc according toclaim 7, comprising the steps of: selecting a video object to be readand presented, reading the selected video object, retrieving and storingmanagement information (NV) from the read video object, presenting theread video object, detecting whether presentation of a video object hascontinued to an end of an interleave unit based on end addressinformation (ILVU_EA) indicative of an interleave unit end addresscontained in the management information (NV), resuming video objectpresentation from a position indicated by a linking information(NT_ILVU_SA) in the held management information when video objectpresentation has been completed to an interleave unit end, accepting aninstruction for selecting a video object (VOB) to be alternativelypresented, determining a presentation start position for thealternatively selected video object according to the angles-specificlinking information (SML_AGLC#1-9_DSTA) in the management information(NV) when a video object change instruction is accepted, and startingpresentation of the alternatively selected video object from adetermined presentation starting position when an angle changeinstruction is received.